It's hard to argue with the improves power and all-weather performance that disc brakes bring to road cycling. It's a given in other cycling disciplines and we have already started to see some big names get important race victories aboard disc brake bikes. Shimano's Ultegra SM-RT800 Disc Rotors feature Freeza technology to cope with the sustained braking and higher temps associated with road cycling. This centerlock rotor continues Shimano's trickle-down technology from Dura Ace that further advances the Ultegra range. Ice-Tech Frezza refers to the hybrid 3-layer sandwich construction of steel and aluminum. The stainless steel adds durability and consistent braking at the surface while the aluminum drops weight and helps dissipate the heat that can build up on long technical descents by up to 50-degrees Fahrenheit. When paired with Ice-Tech pads, temps that would normally be in the 400-degree range operate at a much lower 300-degree number. Lower temperatures improve braking performance and prevent fade for more confident descending.The rotors are available in 140 and 160mm diameters and include a lockring.