The Harken 57mm Double Zircon Block with Becket allows trimmers to quickly adjust sail shapes for varying conditions. At its core, this high-performance block utilizes industrial ceramic ball bearings housed in separate cages to prevent friction and maximize efficiency. Available with 40- and 57-mm sheaves, in single or double blocks, and with or without beckets, this is Harken's most efficient small boat block yet. With a maximum working load of 300 kg (660 lb) and a maximum line diameter of 10 mm (3/8 in), it's a top choice for sailors.