Shimano SM-RT900 Dura Ace Center Lock Rotors: Ice Tech Freeza rotors provide consistent braking performance through energy control, using revolutionary stainless steel and an alloy 3-layer sandwich construction that manages heat while riding. The clad steel/alloy/steel rotor construction allows heat generated from braking, to radiate quickly through the aluminium core dropping the surface temperature around 50. When used with Ice Tech pads the surface temperatures can drop from around 400 to 300, this provides great improvements in all round performance.