Shifting has been even further improved by creating an even more rigid (and lighter) aluminum carrier unit along with re-engineered teeth profile. Cassette design is lighter as Shimano has developed a super lightweight and rigid aluminum cassette sprocket carrier. The largest four cogs are titanium and weight is reduced by 10 grams. Available combinations will be: 11-21T, 11-23T, 11-25T, 11-27T, 11-28T, 12-23T, 12-25T, 12-27T.