Double ball bearing block provides smooth running sheaves for control lines or mainsheets on small boats. Sheave Dia. 1 1/16" (27mm), Thickness 1 1/8" (28mm), Width 1 3/16" (30mm), Length 3 15/32" (88mm), SWL 500 lbs, Weight 3 oz. (85g), Max Line 5/16" (8mm)