Single Block. Computer machined block finished in hardcoat anodized black for durability. Torlon(tm) rollers and Delrin(tm) ball bearings ensure a low-friction aluminum sheave that will handle high loads. Machined center of the block may be used as a " becket" eliminating the need for other blocks. Forged 17-4 high strength D Shackle on a swivel head may be locked in place to eliminate line twist. Flushing holes in each cheek allow easy flushing. Safe Working Load 5000lb(2270kg), Weight 12.0oz (340gm), Max Line 5/8"(16mm), Sheave Diameter 3.2" (82mm), Shackle 5/16" (8mm) 17-4ph, Length 6.3" (160mm), Width 3.2" (82mm)