This sprocket has steel teeth and an aluminium inner part. Both sections are permanentely joined by high strength rivets. This sprockets last at least 3 times longer than any other aluminium sprocket whilst it is half the weight of a normal steel sprocket. The steel teeth also offer greater life for your whole system. Not just the sprocket, but the chain and front sprocket as well. If you are looking for the ultimate in quality and performance, this sprocket will meet your demand.