Single block with aluminum cheeks. Delrin(tm) sheave ensures smooth operation and high safe working load. Sheave Dia. 1 7/16", Thickness 3/4" (19mm), Width 1 9/16" (40mm), Length 3 25/32" (96mm), SWL 1000 lbs (410 kg), Weight 2.4oz. (68g), Max Line 7/16" (11mm)