Utilize Harken's 40 mm Zircon Double Block Becket, Part No. 2193 for a maximum working load of 230 kg (500 lbs) and a maximum line diameter of 8 mm (5/16 in). With a 40 mm sheave (1 9/16 in) and industrial ceramic ball bearings mounted inside caged races, Zircon blocks offer exceptional performance for sail trimming. These bearings are carefully separated to prevent bunching, contact, and interference, making it the most efficient small boat block by Harken. Available in 40- and 57-mm sheaves, in single and double block variations, with or without beckets.