Part No. 344 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)73 mm Length (in)2 7/8 in Weight (g)74 g Weight (oz)2.6 oz Shackle pin (mm)5 mm Shackle pin (in)3/16 in Maximum line (mm)8 mm Maximum line (in)5/16 in Maximum working load (kg)449 kg Maximum working load (lb)990 lb Breaking load (kg)907 kg Breaking load (lb)2000 lb