Harken 57mm Quad Block Swivel with Center Becket is made with a 57mm sheave, suitable for 10mm maximum line diameter and has a maximum working load of 1080 kg (2380 lbs). This low-friction Carbo Air block is dependable, strong, and cost-effective, making it a perfect complement to Harken Big Boat blocks. These compact blocks have remarkable working loads for secure and effortless trimming.