Featuring an impressive 57 mm sheave diameter, the Harken 57mm Triple Fiddle Block Swivel (Part No. HSB379) can support maximum line diameters of up to 6 mm (7/16 in), with a working load of 1080 kg (2380 lb). Made with lightweight, durable Carbo Air materials, these compact blocks are a cost-effective and high-performance companion to Harken's Big Boat blocks. With their exceptional strength and reliability, they make trimming tasks safe and effortless.