Shimano RT-EM910 - W/LOCK RINGSHIMANO RT EM910 disc brake rotors for speed sensor systems deliver powerful and consistent brake performance in all riding conditions. The compact and lightweight ICE TECHNOLOGIES FREEZA rotor significantly reduces heat build up in the brake system to ensure consistent high performance braking even on the steepest downhill stretches. SHIMANO's CENTER LOCK mounting system makes installing and removing rotors quick and easy thanks to the spine mount