Rear Sprocket - Aluminum - 50 Tooth - Purple - Yamaha CNC-machined (not stamped) and feature a computer-aided ultra-light design to reduce unsprung weight and increase power transfer, Rear sprockets made from high-strength, specially enhanced 7075-T6 aluminum that is 33% lighter than steel to further reduce weight and increase power transfer without sacrificing strength, Rear sprockets also feature a special tooth profile that allows the chain to roll easily on and off the sprocket for longer wear, less noise and more power