The Harken 57mm Single Zircon Block with Becket is designed to allow trimmers to quickly adjust sail shapes to changing conditions. Featuring industrial ceramic ball bearings encased in caged races, these blocks maintain efficiency by preventing the bearings from bunching, touching, or stopping each other. Available in 40- and 57-mm sheaves, in both single and double block options, with or without beckets, these blocks are capable of handling a maximum working load of 150 kg (330 lbs) and a maximum line diameter of 10 mm (3/8 in).