The Harken 29mm Clew Block is equipped with Part No. 371, a 29 mm Sheave Ø (in) 1 1/8 in, and has a maximum line Ø and working load of 8 mm (5/16 in) and 150 kg (330 lb) respectively. These reliable and affordable Low-friction Carbo Air blocks are compact and lightweight, making them perfect companions to the Harken Big Boat blocks. With high working loads, they offer safe and easy trimming.