Shimano RT-CL900 Disc Brake RotorQuieter control for any terrain With a focus on decreasing disc brake rotor heat deformation, the result of the new disc brake rotor is quieter than ever brake performance without sacrificing weight or heat dissipation. Quieter than ever, but with superb, consistent braking performance on any long, steep descents thanks to excellent heat dissipation The new arm shape is more robust, leading to quieter operation Heat dissipation paint boosts