The Notch 5/8" Rigging Block with 5/8” Ultra Sling is a small sized lightweight arborist block that accepts working lines up to 5/8” (16mm) diameter Low profile, secure, easy-to-open captive screw pin lock with a high wall, a full diameter and improved anchor sling protection Hot forged aluminum side plates with rope friendly rounded cheeks and precision CNC machined aluminum sheaves with wide bend radii Wide, concave upper sheave with a 5/8” anchor sling. Flared side-plates reduce twisting in complex rigging scenarios. Upper sheave diameter: 1.95 in. (50mm), lower sheave diameter: 2.4 in. (61mm). Working Load Limit: 25 kN (5,620 lbs.), MBS: 125 kN (28,100 lbs.)