Part No. 381 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. Sheave (mm)29 mm Sheave (in)1 1/8 in Length (mm)54 mm Length (in)2 1/8 in Weight (g)34 g Weight (oz)1.2 oz Maximum line (mm)8 mm Maximum line (in)5/16 in Maximum working load (kg)299 kg Maximum working load (lb)660 lb Breaking load (kg)737 kg Breaking load (lb)1625 lb