4-5/8 in. sheave, up to 3/4 in. rope capacity, weighs 7.7 lbs., 4.4 ton working load limit. Green sheave (3/4 in. rope capacity) for easy identification. Spring lock blocks are popular among riggers for their high strength-to-weight ratio and quick-twist rope access. Solid aluminum-alloy cheek plates, bushing, and sheave are supported by stainless-steel axles. For those concerned about aluminum not wstanding the punishment of steel, we have no record of a fracture complaint in 3 years of production. Spring lock blocks have broad cheek plates to protect running lines, and large sheaves to minimize bend in rigging lines (providing 4:1 up to 9:1 ratios).