57mm Carbo Air Block with SwivelLow-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.. Specifications:. Sheave: 57mm / 2-1/4in. Length: 110mm / 4-5/16in. Weight: 87g / 3.1oz. Shackle pin: 5mm / 3/16in. Maximum line: 10mm / 3/8in. Maximum working load: 359kg / 792lb. Breaking load: 1079kg / 2380lb