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 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 2800 lbs (1270kg), Weight 9.0oz (254gm), Max. Line 1/2" (12mm), Sheave Diameter 2.6" (66mm), 5/16" (8mm) Shackle, Length 5.4" (137mm) Width 2.6" (66mm).