Rear Ultralight Sprockets:. Manufactured to extremely tight tolerances from a special material developed to withstand the stress of Supercross, Motocross and Enduro. 7075-T6 aluminum alloy rear chainwheels are 66% lighter than steel, yet incredibly durable. Advanced tooth profile, concentricity and accuracy of fit provide maximum power transfer and long-life. Combination of a very high strength base material and an exceptionally hard-wearing surface result in significantly increased chainwheel life. Self cleaning mud grooves help prevent dirt build-up. Ultralight Silver, 50T, Ultralight