Fiddle block with aluminum cheeks and swivel shackle. Delrin(tm) sheaves ensure low friction and high safe working load. Works with 303-85 for a 4:1 purchase. Sheave Dia. 1 7/16", Thickness 3/4" (19mm), Width 1 7/8" (48mm), Length 5 3/8" (137mm), SWL 1000 lbs (410 kg), Weight 4.4oz. (125g), Max Line 7/16" (11mm)