Harken 57mm Ratchamatic Block Swivel - Part No. 2625 Sheave Ø (mm) 57 mm Sheave Ø (in) 2 1/4 in Max line Ø (mm) 10 mm Max line Ø (in) 3/8 in Max working load (kg) 227 kg Max working load (lb) 500 lb The Carbo Ratchamatic is a load-sensing ratchet block that can rotate freely in both directions under light loads, but automatically engages the ratchet under heavier loads. The transition between ratchet and light-air modes is seamless and effortless, providing a secure grip for medium and light air conditions and delivering a holding power of 10:1.