Fiddle block with swivel shackle and cam cleat. Works with 303-15 for a 3:1 purchase. Delrin(tm) sheaves ensure smooth operation and high safe working loads. Sheave Dia. 1 7/16", Thickness 2 5/16" (59mm), Width 3 1/4" (83mm), Length 5 3/8" (137mm), SWL 1000 lbs (410 kg), Weight 8.9oz. (252g), Max Line 7/16" (11mm)