Shimano's new disc brake calipers retain Shmano's signature control through superior modulation. The BR-M975 retains an opposed two-piston design while reducing weight: The one - piece design is more compact and very stiff which results in a precise and efficient disc brake design. The titanium back plate on the new XTR brake pads are 12 grams lighter than current steel pads. Durability in the pad is also improved by 50%. Use intarnational standard calipers for the ultimate in weight savings to achive the following rotor choices: 160mm / 180mm for the front or 160mm / 140mm for the rear.