This kit includes a Renthal steel front sprocket, a Renthal Twinring rear sprocket and your choice of chain. The Twinring rear sprocket is the longest lasting, most durable offroad sprocket you can buy today. It's unique design and hybrid construction was developed over five years. The Twinring sprocket is made of a 7075 T6 aluminum center with an outher ring of teeth made from Electroless Nickel Coated steel; the outer ring is heated to 200 degrees celsius before fitting to the center, after cooling the two are permanently bonded. The special construction means that this sprocket offers the best of both worlds: the long-lasting durability of a steel sprocket and the light-weight of an aluminum one. Features: Self-cleaning mud grooves between every tooth on both sides to prevent dirt build up. Flat socket head screws add additional strength during side impacts Flat-face design keeps weight to a minimum and makes the Twinring as narrow as a normal sprocket. Precision CNC machined to extremely tight tolerances.