Harken 40mm Carbo Block Single w/Swivel Bracket [2637]40mm Carbo Block Single with Swivel & Bracket Low friction Carbo Air blocks are lightweight, strong, reliableand affordable. Companions to the popular Harken Black Magic block line, these small, compact blocks have very high working loads for safe, easy trimming. Features: Sheave (mm): 40 mm Sheave (in): 1 9 16 in Maximum line (mm): 10 mm Maximum line (in): 3 8 in Maximum working load (kg): 220 kg Maximum working load (lb): 485 lb