Harken's 178mm (7 in.) Big Boat sheave is used for special mainsheet, spinnaker sheet, afterguy/foreguy, or footblock applications as well as a replacement sheave in a Big Boat block. It is made of hardcoat-anodized, PTFE-impregnated 6061-T6 aluminum and features Torlon rollers to carry high radial loads and carbon-black Delrin balls to support sideloads and provide UV protection.
It is designed for a maximum line diameter of 7/8 in. (22mm) and has a maximum working load of 14,000 pounds (6,349kg).