57mm Quad Block Swivel, Center BecketLow-friction Carbo Air blocks are lightweight, strong, reliableand affordable. Companions to our popular Harken Big Boat blocks, these small, compact blocks have very high working loads for safe, easy trimming. Features:Sheave (mm) 57 mmSheave (in) 2 1/4 inMaximum line (mm) 10 mmMaximum line (in) 7/16 inMaximum working load (kg) 1080 kgMaximum working load (lb) 2380 lb