Shimano rt99 ice tech freeza cl disc rotornobody puts more thought into brake rotors than shimano and the sm rt99 xtr race centerlock rotor is proof of that the hybrid steel and aluminum construction saves weight and manages heat buildup even better its been topped off by shimanos lightweight and user friendly centerlock hubrotor interface now you may be wondering what icetech construction actually means or then again why it matters basically icetech rotors consist of two stainless s