Renthal Rear Sprocket Alloy 7075 T6 Grooved - 45T 224U 520Renthal sprockets feature a specially developed nickel chrome molybdenum alloy steel which is case hardened and core refined to give the ultimate combination of strength and hardness. Grooved sprockets have cut outs at the bottom of the tooth to allow the escape of mud that would otherwise be trapped between the sprocket and the chain. This prevents tension from being placed on the chain and the resulting accelerated wear Using advanced computer