High-load, high-strength block has a Universal Circuit (UC) sheave system with multiple friction-reducing bearing components, so the block has considerably less friction than conventional roller blocks, and actually becomes more efficient as you use it. The stainless head swivels or is fixed with a three-way locking fixture. Configuration: Single swivel block Dimensions: 6-9/32"L x 3-1/4"W x 17/32"H Sheave: Aluminum UC for wire or line Ball Bearings: Nomex Teflon high-impact glass-fiber Sheave Size: 3-1/4" Max. Line Diameter: 5/8" (16mm) Max. Wire Diameter: 1/4" Weight: 270z. Cheek Material/Finish: Polished stainless, bolted for easy disassembly Shackle/Strap Type: High-load swivel, forged shackle, stainless straps Safe Working Load: 3,750lb.