The sprocket teeth are made of steel and the central part of aluminium. Both parts are joined permanently together by high-strength rivets. This sprocket has a service life at least three times longer than that of other aluminium sprockets, while it is only half the weight of a conventional steel sprocket. The steel teeth ensure a longer service life for the whole system, i.e. not only the rear sprocket, but the chain and chain wheel as well. If you're looking for the ultimate in quality and performance, this sprocket is the one for you.