Shimano Dura-Ace 7900 10 Speed Rear Cassette:
The Dura-Ace line offers a great combination of durability and lightweight performance. It is available in 8 different sizes from 11-21 up to 12-27.
The largest three cogs on the cassette are supported by a separate cole forged aluminum alloy carrier as are the next two sprockets. This engineering increases stiffness and reduces weight, as does the fact that the four largest cogs, are made from titanium.
The whole cassette weighs in at just 185 grams, perfect for all you weight watchers out there. Shifting performance is smooth it leaves you wondering if you changed gears at all.