The Harken 57mm Ratchamatic Block Swivel, featuring a red 57mm sheave and a maximum line diameter of 10mm (3/8 in), delivers top-notch performance. Its load-sensing ratchet system effortlessly adjusts to low or high loads, providing seamless transitions between ratchet and light-air modes. With a maximum working load of 227kg (500lb), this block is perfect for handling heavy loads with ease.