Harken soft-attach Fly blocks are designed to provide strength without mass, providing sailors with big power in a low-aero package. Designed specifically for high-tech line, these efficient blocks have an incredible working load for their small size. Fly blocks are perfect for use on foiling dinghies and sportboats and for vang cascades and backstay systems on Grand-Prix racers. See also Harken 2161 18mm FLY Block NARROW 18 mm blocks feature an integrated stainless steel inner race and rivet, stainless steel ball bearings, and composite fiber-reinforced sideplates.A length of Spectra® line is included. Sheave Ø (mm)18 mm Length (mm)28 mm Weight (g)7.2 g Maximum line Ø (mm)5 mm Maximum working load (kg)125 kg Breaking load (kg)450 kg