Low-friction 57mm Carbo Air Quadruple Block is lightweight, strong, reliable—and affordable. 30 percent lighter and 60 percent stronger than equivalent blocks. Sideplates are UV-stabilized, high-strength resin. Ball bearings are made from engineered plastic in fitted ball races.The 57mm Carbo Air blocks have an enormous working range that makes them ideal for main and jib sheets, spinnaker halyards and control lines. This range handles loads similar to Harkens 3" standard blocks. Recipient of both the Dame Award and Sail Magazine's Freeman-Pittman Award for innovation.