Shimano rt900 ice tech freeza cl disc rotorthe new rt900 rotor offers even greater heat management capability than shimanos sm rt99 industry leading ice technologies freeza rotors resulting in unparalleled braking performance and reliability in the most demanding conditions this is achieved to the steel braking surfaces with aluminium core with an increased adaptor size heat transfer through the rotor is decreased and more heat can dissipate through the air they are available in a centre loc