Harken 40mm Carbo Air Pivoting Lead Block w/Aluminum Cam-Matic Cleat [2156]40mm Carbo Air Pivoting Lead Block with Aluminum Cam Matic Cleat High strength pivoting lead blocks with cams are used for halyard controls on larger keelboats and as headknockers on dinghies and beachcats for sheeting directly from the boom. Hole spacing and rivet size are the same as Classic models, making upgrades easy. Cam reverses for either up or down cleating. Can be used as becket block. Specifications: Sheave (mm)40 mm Sheave (in)1 9 16 in