Race Spec (RS) Rear Sprockets feature our revolutionary Angled Mud Groove. This exclusive design creates a self-cleaning effect during operation, shedding away mud that would otherwise lead to horsepower loss and sprocket wear. With their precise CNC machining and unique layout, these grooves also allow an increase in tooth surface area of up to 40% over competing sprockets. As a result, contact with the chain is significantly improved, leading to a marked increase in sprocket life over other brands. That's the ProTaper difference.