The Harken 57mm Single Zircon Block (Part No. 2195) has a maximum working load of 150 kg (330 lb) and can handle line Ø up to 10 mm (3/8 in). Its sheave has a diameter of 57 mm (2 1/4 in) and is equipped with industrial ceramic ball bearings mounted within caged races for optimal efficiency. The cages prevent the bearings from bunching, touching, or stopping each other, making this block one of Harken's most efficient choices for small boats. The Zircon block series also includes 40- and 57-mm sheaves in single and double configurations, with or without beckets.