40mm Carbo Air Double Fixed BlockLow-friction Carbo Air blocks are lightweight, strong, reliable-and affordable. Companions to the popular Harken Black Magic block line, these small, compact blocks have very high working loads for safe, easy trimming. Speciications: 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)440 kg Maximum working load (lb)970 lb