Single block with swivel head. Delrin(tm) sheave on plain bearing allows for a low-friction yet high load block. Sheave Dia. 1 1/16" (27mm), Thickness 19/32" (15mm), Width 1 3/16" (30mm), Length 3 1/2" (89mm), SWL 900 lbs, Weight 2 oz. (57g), Max Line 5/16" (8mm)