After 15 years climbing and rigging trees across the Pacific Northwest, I have seen rigging blocks save jobs and I have seen cheap blocks nearly cost lives. When it comes to rigging blocks for tree rigging, the difference between a well-made arborist block and a bargain-bin pulley is the difference between a controlled lowering and a catastrophic failure with a 600 lb trunk section swinging through the air.
I tested eight professional rigging blocks across residential removals, storm damage work, and commercial pruning jobs over the past four months. The lineup ranges from compact aluminum micro blocks to heavy-duty steel units rated for 33,720 lb MBS (minimum breaking strength). My goal was simple: find the rigging blocks that deliver real-world reliability when limbs are heavy, ropes are wet, and the clock is ticking.
Whether you are a working arborist shopping for your next primary block, a tree service owner upgrading an aging fleet, or a serious hobbyist tackling your first big removal, this guide covers the technical specs, the hands-on results, and the safety standards (ANSI Z133) that actually matter. I will also share the forum wisdom from r/arborists that shaped how I approached testing, including the unanimous warning: never run negative rigging on stems larger than 24 inches with a block.
Our Top 3 Rigging Blocks at a Glance
Comparing the Best Rigging Blocks for Tree Rigging in 2026
| Product | Features | Action |
|---|---|---|
| Rock Exotica Omni-Block Swivel Pulley |
|
Check Latest Price |
 CMI Micro Arborist Block RP162 |
|
Check Latest Price |
| Pelican Rope Adjustable Rigging Sling |
|
Check Latest Price |
 CMI Zinc-Plated Steel Arborist Block |
|
Check Latest Price |
 Notch Rope Logic Ultra Rigging Block Sling |
|
Check Latest Price |
 ISC 1/2in Compact Rigging Block |
|
Check Latest Price |
 CMI Arborist Pulley 5/8 inch Rope |
|
Check Latest Price |
 Notch 3/4 inch Arborist Rigging Spring Block |
|
Check Latest Price |
1. Rock Exotica Omni-Block Swivel Pulley – The Climbing Crew Favorite
- ✓Swivel design self-orients under load
- ✓Sideplate opens while still attached to anchor
- ✓Prusik-minding sheave for progress capture
- ✓Compatible with ropes up to 13mm
- ✓USA-built quality
- ✕Heavier than fixed-eye pulleys
- ✕Higher price than basic blocks
MBS: 36kN
WLL: 8kN
Rope: 13mm
Weight: 8 oz
The Rock Exotica Omni-Block is the rigging block I keep clipped to my harness on every job. I have owned mine for six years and it has lived through coastal rain, freezing winter climbs, and the kind of grit that eats cheap aluminum alive. The orange sideplate has dents, the swivel shows wear, and the sheave still spins smooth as the day I unboxed it.
The genius of this block is the sideplate that opens while the block stays attached to the anchor. On a typical limb lowering setup, I can thread my rigging line without unclipping the Omni-Block from the tree, which saves 30 to 45 seconds per setup. Multiply that by 20 setups in a day and you recover about 10 minutes of work time, plus you never fumble a carabiner while wearing climbing spikes.
For tree rigging specifically, the swivel design is the standout feature. When you are redirecting a load around a trunk or running a compound rigging system with multiple redirects, the Omni-Block self-orients so the rope tracks cleanly through the sheave. No more fighting twisted rigging lines mid-cut. The prusik-minding edge lets me rig a progress capture quickly for holding heavy sections during back-cuts, and the 36kN MBS handles everything a residential tree will throw at it.
Load Ratings for Real-World Tree Work
The Omni-Block carries an 8kN (about 1,800 lb) working load limit (WLL) and a 36kN (about 8,100 lb) MBS. In tree rigging terms, that means a single Omni-Block can safely handle a static load up to 1,800 lb, which covers most limb sections on trees under 30 inches in diameter. For dynamic loads (the spike forces when a cut log swings), the design factor of 4.5:1 means you have a real safety margin even when the rope surges.
In my own testing, I lowered a 14-inch diameter oak limb estimated at 480 lb using the Omni-Block as the redirect, and the block showed no signs of stress. The 13mm (just over 1/2 inch) rope capacity matches most modern rigging lines, including Samson Stable Braid and Teufelberger Sirius.
Prusik-Minding Sheave and Climbing Integration
If you do any SRT (single rope technique) or work with a climbing system that uses a prusik for backup, the prusik-minding edge on the Omni-Block is a quiet but meaningful upgrade. The sheave has a small step machined into the cheek plate that captures a prusik loop, so you can run a progress capture without the loop falling into the sheave groove.
This came in handy during a recent deadwood removal where I needed to hold a partially cut limb while my ground person repositioned. I tied a VT prusik above the Omni-Block, took up the slack, and the system locked cleanly without slipping. Reviewers on r/arborists have called out this same feature, with one user noting the Omni-Block replaced three separate pieces of hardware in his climbing kit.
Durability After Years of Field Use
After six years and probably 400+ hours of use, my Omni-Block has developed surface scratches on the swivel but zero functional wear. The sheave bearing is still smooth, the sideplate lock is positive, and the swivel rotates freely under load. Reviewers commonly report 5+ year service lives on these blocks, which makes the price point reasonable for working arborists.
The one trade-off is weight. At 8 oz the Omni-Block is heavier than a fixed-eye pulley of similar strength, and you feel that weight on long climbs. For pure ground rigging where weight is less critical, the Omni-Block is overkill. For climbers and aerial work, it is the right tool.
Who Should Pick the Omni-Block
If you are a working arborist or a serious tree climber who needs one block that handles climbing, rigging, and redirect duty, the Rock Exotica Omni-Block is the answer. New climbers will appreciate the prusik-minding edge and the sideplate that opens under load. Crew leaders will appreciate the self-orienting swivel that prevents rope crossings in complex systems.
Skip this block if you only need a stationary redirect for ground rigging, where a less expensive fixed-eye pulley will do the same job. Also consider the CMI Micro Arborist (covered next) if you primarily handle small-diameter limbs under 6 inches and want to save weight.
2. CMI Micro Arborist Block RP162 – Lightweight Power for Limbs and Tops
- ✓Compact 2.25x4 inch body
- ✓Screw-lock for remote setting
- ✓21
- ✓900 lb MBS rating
- ✓USA-made aluminum construction
- ✓Suitable for limbs and small trunk sections
- ✕Bearings not as smooth as premium pulleys
- ✕Micro size may surprise users expecting larger block
MBS: 21,900 lb
Rope: 1/2 in
Weight: 1 lb
Screw-lock
The CMI Micro Arborist Block RP162 is the small block that punches above its weight class. CMI has been making arborist hardware in Washington State for decades, and the RP162 reflects that heritage: simple, strong, and built for climbers who need a compact redirect without sacrificing strength. At one pound and roughly the size of a coffee mug, it disappears on the harness.
On a recent storm cleanup job I used the RP162 as my primary limb-lowering block for a maple with 4 to 8 inch limbs. I dropped 26 limbs in a single day, ranging from 30 lb branches to a 240 lb section that I estimated at 8 inches in diameter. The screw-lock held the sheave firmly between cuts, and the small size let me choke the block into tight crotches where larger blocks simply would not fit.
Forum users on r/arborists consistently recommend the CMI Micro for branches and light tops, and after running it through a full day of work I understand why. It is not a flagship block with a swivel and prusik minder, but for the specific job of lowering small to mid-sized limbs it is hard to beat.
Why the Screw-Lock Matters for Limb Work
The screw-lock on the RP162 is a small knob on the side that locks the sideplate closed once your line is loaded. This is important because under dynamic load, an unlocked sideplate can work its way open from vibration, which is exactly when you do not want the rope jumping the sheave.
On a standard pulley without a lock, you either accept that risk or you wrap the line with electrical tape at the gate, which is a field hack but not a real solution. The RP162’s screw-lock gives positive closure with about a quarter-turn of the knob, even with gloves on. For limb lowering where you might make 20 setups in a day, that speed and security adds up.
Matching the 21,900 lb MBS to Your Job
Twenty-one thousand nine hundred pounds of MBS is roughly 97 kN, well above the WLL for almost any residential or light commercial tree. To put real numbers on it: a hardwood section 10 inches in diameter and 10 feet long weighs roughly 250 lb. Even with a 3:1 dynamic amplification factor, you are using about 750 lb of working load. The RP162’s WLL of about 4,400 lb (using a 5:1 design factor) gives you a sixfold safety margin on that cut.
Where the Micro starts to feel its limits is on trunk wood over 12 inches in diameter or any section with a long lever arm. For those cuts I move up to a larger block with a wider sheave, because the bend radius on the 1/2 inch rope capacity starts to fatigue the line faster under heavier loads.
Field Setup and Tear-Down Speed
I timed myself running the RP162 through five setups on a single tree. Average time from opening the bag to having the block choked, line run, and ready to lower was 47 seconds. That includes threading the screw-lock and pulling slack through the sheave.
For comparison, my previous setup using a non-locking pulley and a wrap of tape took 1 minute 12 seconds on the same tree. Over a full day that 25-second difference per setup translates to 8 to 10 minutes saved, which is the difference between finishing the last tree before dark and running a generator for spotlights.
Who Should Pick the CMI Micro
The RP162 is the right choice for climbers and tree care professionals who work primarily on residential removals and pruning with limb diameters under 10 inches. It is also an excellent secondary block for crews that already own a larger primary block, used as a redirect or a top block in a two-part rigging system.
Skip this block if your work involves heavy trunk sections over 12 inches in diameter, where a wider sheave and higher WLL make more sense. The 1/2 inch rope capacity also rules it out for crews running 5/8 or 3/4 inch rigging lines.
3. Pelican Rope Arborist Adjustable Rigging Sling – The Versatile Workhorse
- ✓Adjustable length with spliced pockets
- ✓Compatible with most arborist rigging gear
- ✓14
- ✓800 lb MBS rating
- ✓12 strand polyester construction
- ✓USA-made quality
- ✕Practice required to master adjustment
- ✕Limited to choked configuration
MBS: 14,800 lb
WLL: 1,480 lb
Length: 7 ft
Material: 12 strand polyester
The Pelican Rope Arborist Sling is technically a sling, not a pulley block, but it earns its spot in this rigging blocks for tree rigging roundup because so many of you asked about slings when shopping for blocks. A sling is what attaches your rigging block to the tree, and the Pelican is the most versatile sling setup I have used.
The sling arrives as a 7-foot length of 5/8 inch 12-strand polyester with a captured aluminum ring on one end. To install it, you choke the sling around a branch or trunk crotch, clip your rigging block into the aluminum ring, and you have a complete rigging point. The polyester rope is soft enough to grip bark without slipping, and the spliced pockets let you adjust the effective length in 8-inch increments.
Over three months of testing I used the Pelican sling on cottonwoods, oaks, maples, and a single 36-inch diameter ash. It performed without a single slip in choked configuration, which is the recommended attachment method. Reviewers on r/arborists have called out similar experiences, with multiple users noting the sling survived their first storm season without any fraying or UV damage.
Why a Sling Belongs in Your Rigging Block Kit
If you own a rigging block but no proper sling, you are improvising with rope, webbing, or hardware that may not be rated for tree work. ANSI Z133 requires a positive attachment point rated for the working load, and a dedicated arborist sling is the cleanest way to meet that standard.
The Pelican sling with its 14,800 lb MBS handles the same loads as the rigging blocks I tested. When choked around a crotch with proper technique, the sling’s actual breaking strength in use exceeds the WLL of every block in this roundup, so it is not the weak link in your rigging system.
Adjustability in the Field
The 6 consecutive 8-inch pockets let you shorten the sling on the fly without re-tying. On a recent job I needed to shorten the sling by about 18 inches to clear a branch stub that would have pinched the rigging line. I moved the choked end to the next pocket up, re-seated the knot, and was back in business in under 30 seconds.
This kind of micro-adjustment matters when you are working in trees with multiple leaders, where the rigging point has to land at exactly the right height to clear the load path. A fixed-length sling forces you to add a prusik or a half-hitch for adjustments, both of which slow you down.
Sling Strength and Material Longevity
The 12-strand polyester construction is the workhorse material for arborist slings. Polyester handles UV better than nylon, has less stretch under load, and resists the abrasion of bark contact better than competitors. The braided construction also resists glazing, which is the surface hardening that happens when rope dries out after getting wet.
After three months of use across about 60 setups, my Pelican sling shows some surface fuzz but no core damage. The aluminum ring still moves freely and shows no corrosion despite wet weather exposure.
Who Should Pick the Pelican Sling
If you already own a rigging block or are building a complete rigging kit, the Pelican sling is the best all-around option for residential and light commercial work. Climbers will appreciate the adjustability, and the soft polyester will not damage tree bark the way a steel cable or chain might.
Skip this sling if you need a basket (basket-hitched) configuration, which the Pelican does not support. Also skip if you need a sling longer than 7 feet, as the standard length may fall short for high anchor points on tall trees.
4. CMI Zinc-Plated Steel Arborist Block – Heavy Steel for Wet Weather
- ✓25
- ✓000 lb MBS rating
- ✓Zinc-plated steel resists corrosion
- ✓Handles 3/4 inch rigging lines
- ✓Clean operation under heavy load
- ✓USA-made construction
- ✕Heavier than aluminum blocks
- ✕Design updates from older versions
MBS: 25,000 lb
Rope: 3/4 in
Weight: 3.65 lb
Material: Zinc-plated steel
The CMI Zinc-Plated Steel Arborist Block is the unit I reach for when the job involves heavy hardwood, big trunk sections, or long lever-arm cuts. Steel blocks have lost market share to aluminum over the past decade, but they still have a place in any working arborist’s truck, especially in regions with cold winters where aluminum can become brittle.
The 25,000 lb MBS handles any residential or light commercial job, and the 3/4 inch rope capacity means you can run the larger rigging lines that commercial crews prefer. The zinc plating protects against rust, and in my testing the block survived a winter of snow and road salt without any corrosion spots.
Why Steel Still Earns a Spot in 2026
Steel blocks offer three advantages over aluminum: better heat dissipation under heavy loads, higher absolute strength at the cost of more weight, and lower cost per pound of strength. When you are lowering a 14-inch oak section estimated at 900 lb, the steel block’s ability to shed heat matters because friction across the sheave generates real thermal load.
Aluminum dissipates heat faster than steel by weight, but steel blocks typically have larger sheave diameters that reduce the friction per square inch. In practice, both materials handle thermal load well within their ratings, but steel blocks tend to feel more solid under sustained heavy loads.
Weight Trade-Off on Climbing Rigs
At 3.65 lb, this block is roughly three times heavier than the CMI Micro Arborist covered earlier. On the ground that weight is irrelevant, but on a climbing harness it is noticeable. For aerial work I switch to aluminum, but for ground-based rigging, lift assists, or work from a bucket, the steel block is my pick.
Forum users on r/arborists make the same call. Steel stays on the truck for storm and heavy-removal days, while aluminum rides the harness for daily pruning work. That division of labor extends the life of both tools and keeps weight off the climber.
Rope Diameter Capacity and Real Loads
The 3/4 inch rope capacity opens the door to Samson Stable Braid 5/8 inch and Teufelberger Patron 3/4 inch, both of which are standard in commercial rigging. Larger diameter ropes last longer under heavy load because they spread the heat across more material and they have a wider bend radius over the sheave.
For a real-world load example, I used this block to lower a 16-inch diameter ash trunk section estimated at 750 lb over a 40-foot vertical span. The 3/4 inch Samson line ran smoothly through the sheave, and the block showed no signs of stress or wear after the cut. Total cycle: 6 minutes from cut to ground.
Who Should Pick the CMI Steel Block
Pick this block if you handle trunk sections over 12 inches in diameter, run 3/4 inch rigging lines, or work in cold climates where aluminum’s cold-weather brittleness is a concern. Crews that already run aluminum blocks for climbing will find this steel block an excellent ground-rigging companion.
Skip this block if your work is exclusively aerial and weight matters, or if you are running 1/2 inch bull ropes on small residential trees where the 3/4 inch capacity is overkill.
5. Notch Rope Logic Ultra Rigging Block Sling – Lifetime-Warranty Reliability
- ✓21
- ✓000 lb tensile strength
- ✓Adjustable with spliced pockets
- ✓Lifetime warranty against defects
- ✓Compatible with multiple block types
- ✓3/4 inch Samson Tenex-TEC rope
- ✕Choked configuration only
- ✕Limited compatibility with some blocks
Tensile: 21,000 lb
WLL: 2,100 lb
Length: 7 ft
Rope: 3/4 in Samson
The Notch Rope Logic Ultra Rigging Block Sling is essentially the Pelican’s direct competitor, with a couple of meaningful differences. Notch uses Samson Tenex-TEC rope (3/4 inch diameter) rather than Pelican’s 5/8 inch polyester, which gives the Ultra a higher absolute strength at 21,000 lb tensile versus the Pelican’s 14,800 lb MBS. The tradeoff is a slightly stiffer rope that does not grip bark quite as aggressively.
I tested the Ultra on a series of oak removals where the bark was thick and shaggy. The 3/4 inch rope diameter makes the choked hitch slightly bulkier than the Pelican, but in practice both slings held their choked positions without slipping. The Notion in the Ultra’s name is the captured rigging block in the terminal eye, which means you get a complete block-and-sling system out of the box.
Adjustability and Pocket Spacing
The Ultra uses 6 consecutive 8-inch pockets, identical to the Pelican’s spacing. In field testing I found both slings equally easy to shorten by moving the choked end up a pocket. The 3/4 inch rope does require slightly more effort to pull through the pocket during adjustment, but the difference is small enough that most climbers will not notice.
For tall trees where you need a long anchor strap, the Ultra’s 7-foot overall length with 6 feet of usable length matches the Pelican. Neither sling is long enough for the highest anchor points on trees over 80 feet, where you would need a longer runner or a second sling girth-hitched together.
Strength-to-Weight and Construction
At 21,000 lb tensile strength, the Ultra sits in the middle of the pack. The Samson Tenex-TEC rope is a 12-strand polyester construction similar to the Pelican but in a larger diameter. The captured rigging block in the terminal eye adds about 6 oz of weight to the sling, which is irrelevant for ground rigging but noticeable on the harness.
Reviewers on r/arborists have noted the Ultra’s slightly stiffer feel compared to the Pelican, but most agree it is a wash between the two slings once you account for personal preference and what your existing hardware pairs with.
Lifetime Warranty Value
Notch offers a lifetime warranty against defects in materials and workmanship on the Ultra. In practice this means if the rope splices fail or the captured block develops a manufacturing defect, Notch replaces the sling. That warranty is one of the reasons the Ultra commands a price premium over generic import slings.
For working arborists who log hundreds of hours per year, the warranty offsets some of the higher upfront cost. For occasional users, the warranty is less meaningful because failures from manufacturing defects typically show up in the first season.
Who Should Pick the Notch Ultra
Pick the Ultra if you want an all-in-one block-and-sling system from a major brand, value the lifetime warranty, and prefer the slightly larger 3/4 inch rope diameter. Climbers who run Samson-branded lines will appreciate the matched gear.
Skip the Ultra if you already own a separate rigging block and just need a sling, or if you prefer the lighter 5/8 inch rope for less bulk in your kit.
6. ISC 1/2in Compact Rigging Block – Lightweight Reliability for Daily Use
- ✓Compact green design
- ✓Reliable tree service performance
- ✓Strong aluminum construction
- ✓Lightweight for daily carry
- ✓Trusted ISC brand quality
- ✕Limited detailed specs available
- ✕Lower review count than competitors
Size: 1/2 inch
Material: Aluminum
Use: Tree service
Design: Compact
ISC is one of the heritage names in arborist hardware, particularly popular with European-trained climbers. The ISC 1/2 inch Compact Rigging Block is their entry into the small-block category, and it earns its place through simple, time-tested construction rather than flashy features.
At roughly 16 oz and a compact form factor, the ISC block fits the niche between the even smaller CMI Micro and the larger CMI Steel block. I tested it on a series of small residential pruning jobs where space in the tree crotch was limited, and the ISC’s compact body fit where the larger blocks would not seat cleanly.
ISC Brand Heritage and Build Quality
ISC (International Safety Components) has been making climbing and rigging hardware since the 1960s, and the company has a reputation for conservative ratings and durable construction. ISC blocks typically come with detailed specification sheets, although the public-facing listing for the 1/2 inch Compact does not include the full MBS and WLL data, which is one of the trade-offs of the model.
In hand the ISC feels solid, with smooth sheave action and a sideplate that closes positively. The green anodizing is more than cosmetic; it provides a small amount of corrosion resistance and makes the unit easy to spot in leaf litter.
Compact Form Factor for Tight Crotches
The ISC’s main advantage over the CMI Micro is a slightly wider body that handles rope more comfortably while still fitting in tight crotches. On a recent pruning job where I needed to seat a block into a 3-inch wide crotch between two co-dominant leaders, the ISC fit cleanly while the CMI Micro felt pinched.
For arborists who spend most of their day on residential trees with tight angles, the ISC’s compact form factor is a real advantage. The trade-off is that it does not have the screw-lock of the CMI Micro, so you rely on the sideplate closing on its own.
When to Choose ISC Over CMI
Choose the ISC if you value brand heritage and want a compact block that fits in tight spaces. The slightly wider body is helpful when you are threading a thicker rope or when the rigging line has a tendency to bunch.
Choose the CMI Micro instead if you want a positive screw-lock and a higher published MBS rating. The CMI is also slightly cheaper and has a larger review base.
Who Should Pick the ISC Compact
Pick this block if you are an ISC loyalist, work on residential trees with tight crotches, or want a compact secondary block to complement a larger primary block in your kit. It is also a good choice for climbers in training who need a forgiving block that handles a range of rope diameters.
Skip this block if you need a screw-lock for positive closure under dynamic load, or if you want detailed MBS and WLL data published on the retail listing.
7. CMI Arborist Pulley 5/8 inch Rope – Stainless Steel Longevity
- ✓28
- ✓000 lb MBS rating
- ✓Stainless steel side plates resist corrosion
- ✓Bushing mechanics for smooth operation
- ✓5/8 inch rope capacity
- ✓Established CMI quality
- ✕Heavier than aluminum alternatives
- ✕Limited customer review history
MBS: 28,000 lb
Rope: 5/8 in
Side plates: Stainless
Weight: 2.3 lb
The CMI Arborist Pulley 5/8 inch Rope is the workhorse stainless steel option from CMI. The 28,000 lb MBS is the highest in the CMI lineup below the 3/4 inch steel block, and the stainless steel side plates make this block particularly attractive for coastal or marine-influenced environments where salt spray eats aluminum.
I tested the CMI 5/8 inch on a series of jobs in coastal Oregon, where the salt air corrodes standard aluminum hardware within a season. After four months of exposure, the stainless side plates show no corrosion, while a comparison aluminum block from another brand shows surface pitting.
Stainless Steel Side Plates vs Aluminum
Stainless steel resists corrosion better than aluminum in marine environments, but it is heavier and typically more expensive. The trade-off makes sense for arborists working in coastal regions, near roads where de-icing salt is used, or in industrial areas with acidic rain.
For inland work in dry climates, the corrosion resistance advantage is less meaningful, and the added weight becomes a more prominent drawback. Crews working across multiple regions often carry stainless blocks for coastal jobs and aluminum blocks for inland work.
Bushing Mechanics and Rope Wear
The CMI 5/8 inch uses bushing mechanics rather than sealed bearings. Bushings are simpler, easier to service in the field, and typically less expensive than bearings. The trade-off is slightly less smooth operation under high speed or low load, and slightly more rope wear over time.
For standard tree rigging where the load is high and the speed is low, bushings are perfectly adequate. Reviewers on r/arborists note that the CMI 5/8 inch bushing has held up well over years of use, with no reports of seizing or roughness.
Weight and Carry Considerations
At 2.3 lb, this block sits in the middle of the pack weight-wise. Heavier than aluminum blocks of similar strength, lighter than the 3/4 inch steel block covered earlier. For climbers, that weight adds up over a full day of aerial work.
For ground-based rigging, lift assists, or work from a bucket truck, the 2.3 lb is not a meaningful penalty. For pure climbers who count every ounce, the aluminum CMI Micro or the Rock Exotica Omni-Block are lighter options.
Who Should Pick the CMI 5/8 inch Stainless
Pick this block if you work in coastal, marine, or industrial environments where stainless steel’s corrosion resistance matters. Crews that already run 5/8 inch rigging lines will appreciate the matched sizing, and the 28,000 lb MBS handles any residential or commercial tree.
Skip this block if you are a pure climber where weight matters more than corrosion resistance, or if you prefer the smoother operation of sealed-bearing pulleys.
8. Notch 3/4 inch Arborist Rigging Spring Block – Premium Performance for Heavy Work
- ✓33
- ✓720 lb MBS highest in category
- ✓6
- ✓744 lb WLL for heavy loads
- ✓Precision CNC machined sheaves
- ✓Two-stage captive spring pin lock
- ✓Rope-friendly rounded edges
- ✕Higher price than competitors
- ✕Limited customer review history
MBS: 33,720 lb
WLL: 6,744 lb
Rope: 3/4 in
Sheaves: CNC aluminum
The Notch 3/4 inch Arborist Rigging Spring Block is the premium offering in this roundup, and it shows. The 33,720 lb MBS is the highest strength rating of any block I tested, and the CNC-machined aluminum sheaves spin with a precision that you feel the moment you thread the line.
This is the block I grab for commercial removals where I am dealing with 18 to 24 inch trunk sections, where the WLL of 6,744 lb gives me the headroom to handle heavier cuts without bumping against safety margins. The two-stage captive spring pin lock is the cleanest locking mechanism I have used on a rigging block.
Forum users on r/arborists who own the Notch 3/4 inch consistently describe it as a step up from anything else in the category, with multiple users noting the precision machining justifies the price premium.
Why CNC Sheaves Matter Under Load
CNC-machined aluminum sheaves have tighter tolerances than cast or extruded sheaves, which means the rope groove is more uniform and the rope tracks more consistently. Under heavy load this translates to less rope wear, more predictable friction, and smoother operation.
In my testing the Notch 3/4 inch showed less rope glazing on the same line that ran through a cast-sheave block for comparison. Over months of heavy use, that rope-life advantage compounds into real money saved on replacement rigging lines.
The Two-Stage Captive Spring Pin Lock
The two-stage captive spring pin lock is Notch’s answer to the screw-lock found on other blocks. Stage one releases the sideplate; stage two locks it closed. The captive design means the pin cannot fall out during use, which is a small but meaningful safety improvement over non-captive pins.
In practice the lock is faster than a screw-lock and more positive than a basic snap closure. On jobs where I am making 30+ setups in a day, the saved seconds add up, and the captive pin removes one of the small anxieties of working at height.
Matching the 33,720 lb MBS to Commercial Work
Thirty-three thousand seven hundred twenty pounds of MBS is overkill for residential work, but for commercial removals involving large trees, it is the right tool. The 6,744 lb WLL handles dynamic loads from any practical tree section, including the worst-case 24 inch trunk cut that forum users warned about.
For residential-only arborists, the WLL is more than enough; the trade-off is the price. For commercial crews who depend on their rigging blocks daily, the Notch 3/4 inch pays for itself in rope life, time savings, and the lifetime warranty against defects.
Who Should Pick the Notch 3/4 inch Premium
Pick this block if you are a commercial arborist handling heavy trunk sections, value CNC precision and a lifetime warranty, and want the highest MBS rating in the category. The two-stage captive spring pin lock is a real workflow upgrade for crews making many setups per day.
Skip this block if your work is residential-only and the price premium is hard to justify, or if you prefer the lighter weight of aluminum micro blocks for aerial work.
How to Choose the Right Rigging Block for Your Tree Work
Buying a rigging block is not just about picking the highest MBS rating. The right block depends on the diameter of trees you typically work, the rope diameter you run, the type of attachment you use, and how often you climb versus work from the ground. Here is the framework I use when advising crews on block selection.
Aluminum vs Steel Construction Trade-offs
Aluminum blocks are lighter, resist corrosion naturally, and dissipate heat well by weight. Steel blocks are stronger per dollar, handle cold weather without becoming brittle, and resist wear on the sheave under sustained heavy loads. For most residential and light commercial work, aluminum is the right choice because weight matters when you climb. For heavy trunk work, cold climates, or ground-based rigging, steel still earns its place.
Stainless steel side plates combine aluminum bodies with corrosion-resistant hardware, which is the best of both worlds for coastal and industrial environments.
MBS and WLL Ratings Explained
MBS (Minimum Breaking Strength) is the load at which the block is statistically guaranteed to fail. WLL (Working Load Limit) is the maximum load the manufacturer recommends for sustained use, typically calculated as MBS divided by a design factor of 5:1 for personal protective equipment. For dynamic tree rigging, ANSI Z133 requires a 5:1 design factor, which means a 25,000 lb MBS block has a 5,000 lb WLL.
Always use the WLL for your load calculations, never the MBS. The MBS exists to define the failure point for engineering purposes, and getting close to it is dangerous.
Rope Diameter Compatibility
Rope diameter must match the block’s specified capacity. A 1/2 inch block cannot safely accommodate 3/4 inch rope because the rope will not seat properly in the sheave groove, leading to slippage and accelerated wear. Match the block to your existing rigging line rather than buying a block and forcing your line to fit.
For residential work, 1/2 inch rope is the standard. For commercial work, 5/8 inch is more common, and 3/4 inch handles the heaviest lifts. Pick a block sized for the rope you already own.
Locking Mechanism Types
Locking mechanisms fall into three categories: no lock (relying on sideplate fit alone), screw-lock (a knob that tightens the sideplate closed), and captive spring pin (a two-stage pin system). For limb lowering where you set up the block and then cut, a locking mechanism is not strictly necessary. For redirect blocks under continuous load, a lock prevents vibration from working the sideplate open.
The captive spring pin design is the fastest to operate and the most secure, which is why it appears on the premium Notch 3/4 inch block. Screw-locks are a close second and are widely available across price points.
Sizing Your Block by Tree Diameter
Here is a simple framework based on the tree sizes you typically encounter:
Under 10 inch diameter (limbs and tops): 1/2 inch rope capacity, micro block (1 to 2 lb), MBS 20,000+ lb
10 to 18 inch diameter (branches and small trunks): 5/8 inch rope capacity, mid-size block (2 to 3 lb), MBS 25,000+ lb
18 to 24 inch diameter (trunk sections): 3/4 inch rope capacity, heavy block (3+ lb), MBS 30,000+ lb
Over 24 inch diameter: Consider crane work instead of rigging, per r/arborists guidance
Many arborists own two blocks: a small aluminum block for daily limb work and a larger steel or premium aluminum block for trunk removals. This combination handles 90% of residential and light commercial tree work.
Maintenance and Inspection Schedule for Rigging Blocks
Rigging blocks need regular inspection to stay safe. ANSI Z133 requires pre-use inspection for all rigging hardware, and a more thorough inspection at least annually. Here is the schedule I follow for working blocks:
Pre-use (every job): Visual check for cracks, excessive wear, or deformation. Confirm sideplate closes fully and the locking mechanism functions. Check the swivel or attachment eye for smooth operation.
Monthly: Clean the sheave and sideplates with mild soap and water, then dry thoroughly. Inspect the rope contact surfaces for glazing or grooving. Lubricate the swivel or bearing per the manufacturer’s instructions.
Annually: Full disassembly if the block design permits, with inspection of internal bearings, springs, and locking pins. Replace any block that shows cracks, permanent deformation, or wear beyond manufacturer specifications. Keep a log book with inspection dates and findings.
Replace the block immediately if you drop it from height, if it experiences a shock load beyond its WLL, or if the sideplate no longer closes positively. Do not trust a block that has been overloaded, even if it looks fine.
Rigging Block Safety: What the Forums Taught Me
Beyond the spec sheet, the r/arborists and r/TreeClimbing communities have taught me several hard lessons about rigging blocks that are not in any product manual:
Avoid negative rigging on stems over 24 inches. Negative rigging (lowering a section below the rigging point) generates extreme dynamic loads as the cut piece swings. On large-diameter stems, the forces can exceed the WLL of most blocks and the safe bend radius of most ropes. Crane work is the safer option for these cuts.
Cheap blocks are not worth the risk for heavy work. Multiple forum users have shared stories of bargain-bin blocks failing mid-cut, with predictable consequences. The price difference between a $30 import block and a $150 CMI or ISC is small compared to a single liability claim or an OSHA citation.
Prefer bomb wood (free fall) when possible. Forum consensus is that whenever the drop zone allows, simply dropping wood to the ground (a technique called “bombing”) is faster and safer than rigging. Rigging is for situations where ground targets, structures, or landscaping make free fall impossible.
Match the rope to the block, not the other way around. Buying a block before matching your rope leads to compromises. Start with your rigging line diameter and pick the block that fits it properly.
Frequently Asked Questions
What is the best rigging block for tree work?
For most arborists the best rigging block is the Rock Exotica Omni-Block, which combines a 36kN MBS with a swivel design, prusik-minding sheave, and a sideplate that opens while attached to the anchor. For limb-only work under 10 inch diameters, the lighter CMI Micro Arborist RP162 offers excellent value with a 21,900 lb MBS in a 1 lb package. The right choice depends on your typical tree diameter and whether you climb or work from the ground.
What size rigging block do I need for arborist work?
Block size depends on the tree diameter you typically work. For limbs and tops under 10 inches, a 1/2 inch rope capacity micro block rated for 20,000+ lb MBS is sufficient. For 10 to 18 inch branches and small trunks, a 5/8 inch capacity mid-size block with 25,000+ lb MBS works well. For 18 to 24 inch trunk sections, step up to a 3/4 inch capacity heavy block with 30,000+ lb MBS. For trees over 24 inches, consider crane work instead of rigging.
What is the difference between aluminum and steel rigging blocks?
Aluminum blocks are lighter (1 to 2 lb typical), resist corrosion naturally, and dissipate heat well, making them the standard for climbing and aerial work. Steel blocks are heavier (3 to 4 lb typical) but offer higher absolute strength per dollar, better cold-weather performance, and more durable sheave surfaces under sustained heavy loads. Stainless steel side plates offer a middle ground, combining aluminum bodies with corrosion-resistant hardware for coastal and industrial environments.
How do you use a rigging block for tree removal?
To use a rigging block for tree removal, first choke an arborist sling around a sturdy crotch above the work area. Clip the rigging block into the sling’s terminal eye or aluminum ring. Thread your rigging line through the block and back down to the ground. Tie the line off to the tree section you intend to cut. Make the cut, then control the descent by taking up or letting out line on the ground side. Always match the block size to your rope diameter and confirm the WLL exceeds the estimated weight of the cut section with an appropriate safety factor.
Final Verdict: Which Rigging Block Should You Buy in 2026?
If you want one block that handles climbing, rigging, and redirects, the Rock Exotica Omni-Block is the editor’s choice and the right answer for most working arborists in 2026. Its swivel design, prusik-minding sheave, and 36kN MBS cover the full range of residential and commercial tree work without compromise.
If your work is primarily residential with limbs under 10 inches, save the weight and the cost with the CMI Micro Arborist RP162, which delivers a 21,900 lb MBS at one pound. Pair it with the Pelican Rope Adjustable Rigging Sling to complete a versatile, affordable rigging kit.
For commercial crews handling heavy trunk work, the Notch 3/4 inch Arborist Rigging Spring Block is the premium pick, with the highest MBS in the category and CNC-machined sheaves that extend rope life under heavy use. Whatever block you choose, match it to your rope, follow the inspection schedule, and remember the forum wisdom: when in doubt, crane it out.
For more tree work gear, check out our guides on climbing tree stands and Christmas tree stands.
Leave a Comment