The XTR RT-98 rotor looks and feels like a standard rotor. In this case looks can be deceiving. The rotor uses what Shimano calls Ice-Tech technology, meaning the rotor is clad with two different materials They feature an aluminum core sandwiched in stainless steel.
The alloy core offers heat management - keeping the rotor cooler and radiation performance - to dissipate heat quicker. In short, the Ice-Tech keeps the rotor cooler than a standard stainless steel rotor providing less noise and fade as well as increasing pad life.
Rounding out the rotor is an anodized alloy spider, which again dissipates heat far better that a one piece stainless unit and saves weight. When you compare this product to other rotor designs on the market, it becomes apparent that Shimano has really put a lot of time and thought into the M980 series braking system.