Shimano puts a lot of effort into developing tech in the rotor market and the SM-RT99 rotor is proof of that fact.
A steel and aluminum hybrid construction saves weight and dissipates heat extremely well. Topped off by Shimano's lightweight, user-friendly, CenterLock hub interface provides an extremely light and powerful braking system.
What is IceTech? IceTech rotors consist of two stainless steel braking tracks that are bonded to an aluminum inner-core. Serious heat distribution providing consistent braking performance through energy control, the clad steel/alloy/steel rotor construction allows heat generated from braking to radiate quickly through the aluminium core achieving surface temperature drops of around 50 deg C. Paired with IceTech pads surface temperatures can drop from around 400 to 300 deg C, this provides great improvements in performance.