They are made of a special composite of aluminium and ceramic material and called Ceradure. These lightweight rotors for disc brakes have applications beyond bikes. As a matter of fact the bike rotors complete a development stage that started with cars for the famous Paris-Dakar Rally.
Ceradure rotors are also being used for Powered Two-Wheelers. Two years ago the development of Ceradure rotors for bikes started. That resulted in a 203 mm rotor that comes in at 97 grams, among other models. Now Ceradure is ready to deliver its rotors to OEMs as well as the Aftermarket.
Photo Bike Europe