Because of their high load capability, the 57mm Carbo AirBlocks have an enormous working range. Use for main and jib sheets on centerboard and keelboats such as Lightings, Dragons, Solings and J/24s. Features include the ""Cam-Lock"" locking system on singles, beckets, doubles and triples, and the Ti-Lite system on singles. Attachment applications and uses are limitless. Just use your imagination! The footblock attaches easily with three 3/18 inch (5mm) screws and is pressed together to prevent the balls from coming out. 7/16 in LINE, MWL 792#, BS 2380# WT. 2.5OZ SHEAVE 21/4".