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ISC Medium 3/4" Spring Block

 ISC Medium 3/4”  Aluminum Arborist Block  The upper sheave and screw are captive - no chance of losing pieces in the tree. Block accepts 1” slings and 3/4” ropes Save on a combo sling & block kit
ISC Medium 3/4 Aluminum Spring Block image ISC Medium 3/4" Aluminum Spring Block

Buy ISC Medium 3/4" Block

Block with 3/4” x 8’ Loopie

The ISC medium arborist block is a great tree rigging block for professional use. This block is built for serious use with practical features that set it above other tree rigging blocks. The upper sheave is over-sized so that it can accept up to 1” tree rigging slings. The block is secured with a spring-lock. To open, the user simply pushes the pin in, twists, and the sideplates may be swung open. The upper bushing and pin are retained, so they can't fall out during use.

The block accepts rigging ropes of up to 3/4” diameter, and tree rigging slings up to 1”. The load rating on the block is 33,720 lb MBS (150 kN), with a WLL of 6,744 lb (30 kN) at a 5:1 design factor. The surfaces of this block are rounded to be more rope-friendly. The sheaves are larger than other 3/4” block for a better bend radius in your rigging lines.

This arborist block is recommended for professional use in medium to heavy tree rigging. The combination of good design and strength is unbeatable at this price.

Purchase this kit as a package with a 3/4” x 2’-8’ Loopie sling and save.


Video Overview by Niceguydave

  • Oversized upper sheave accepts 1” slings
  • Captive upper sheave with spring-lock
  • Wide bend radius on lower sheave
  • Improved machining for rope-friendly surfaces
  • Sintered bronze bushings
  • Powder-coated side plates
Made in: UK
MBS: 33,720 lb / 150 kN
WLL (5:1) / (10:1): 6,744 lb / 3,372 lb
Max Rope Diameter:3/4”
Max Sling Diameter: 1”
Sideplate Material:Powder-coated aluminum
Sheave Material:Aluminum
Axle Material: Stainless Steel
Upper Sheave Diameter: 2”
Lower Sheave Diameter: 3 1/2”
Height: 8.75”
Width: 4.75”
Weight: 4.77 lb

Each ISC Medium 3/4” medium arborist block is individually serial-numbered.


  • CE Approved

ANSI Z133-2017

The American National Standards Institute (ANSI) has released the ANSI Z133 safety requirements which apply to arboricultural operations. Components of a rigging system must be used within their Working Load Limits.

ISC blocks are ANSI compliant when used within the manufacturer Working Load Limits.

A green log weight chart (found in the Samson Rigging Wheel) will aid in determining loads in tree rigging.

The full ANSI Z133 safety requirements are available on our tree care standards page.

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