The Shimano Dura-Ace SM-RT900 Rotor prevents brake fade on extended descents where you'd normally experience a major decrease in stopping power on the road. This Freeza Rotor is part of Shimano's newest Dura-Ace hydraulic disc brakes, meaning they're compatible with the Dura-Ace BR-R9170 caliper and Ice-Tech pads. They're compatible with frames that accommodate flat-mount disc brakes and attach to Shimano's proprietary Centerlock hub system. The 3-layer rotor construction has a stainless steel braking surface with an alloy core featuring finned cut-outs for effective heat dispersion. Shimano claims heat is reduced by up to 50-degrees Celsius, which is significant when you're riding along mountainous terrain where sustained descents pose a threat to your stopping power.