Brilliant Single Stainless Steel Block with Universal Head. Aluminum UC sheave runs on Nomex/Teflon bearing as well as Delrin Ball Bearings for low friction and high strength. For Boats to 48'. Sheave Dia. 3 1/4", Thickness 1 7/32", W 3 1/4", L 6 19/32", SWL 3750 lbs, Weight 1lb 11oz, Max Line 9/16".