Shimano Dura-Ace CS-7700 9-speed Cassette

"Three precision-made light alloy sprocket carriers reduce weight while increasing sprocket stiffness. The use of both titanium and chromoly keeps weight down, maintains strength, and assures maximum torque response. Lightweight 9-speed sprockets provide a wider gear choice while weighing approximately the same as the previous 8-speed cluster. Sizes: 11-21, 11-23, 12-21, 12-23, 12-25, 12-27. Wt: 159.5 g (12-23)."