Series 55 RT Ratchet Orbit Blocks feature 20:1 holding power and are the only ratchet blocks available that can be set in manual mode or full automatic engagement mode. Essential equipment on racing dinghies and sportboats, when you want the most holding power you can get. Sheave: Carbon-fiber-reinforced, PTFE impregnated engineered nylon Ball Bearings: High-compression-strength carbon black Acetal; Stage 2 Bearing: Glass-fiber-reinforced, MoS2 impregnated engineered nylon Cheek Material/Finish: Toughened glass-fiber-reinforced nylon Shackle/Strap Type: UV-stabilized, multi-strand Dyneema rope link