The Notch 1/in. Rigging Block is a small sized light-weight arborist block accepts working lines up to 1/in. (13 mm) diameter. Hot forged aluminum side plates with rope friendly rounded cheeks. Precision CNC machined aluminum sheaves with wide bend radii. Stainless steel axle. Low profile, secure, easy to-open captive screw pin lock. High wall, full diameter, improved anchor sling protection. Wide, concave upper sheave accepts 5/8 in. anchor slings. Flared side-plates reduce twisting in complex rigging scenarios. Upper sheave diameter: . 75 in. (19mm), lower sheave diameter: 1. 5 in. (38 mm). Working Load Limit: (WLL) 20 kN (4,496 lbs ), MBS: 100 kN 22,480 lbs.