Shimano Dura Ace RD7900 Rear Derailleurs. The new design is compatible with wider range cogsets and can accommodate a maximum 28 tooth cog. The available wider range creates even better compatibility with compact cranksets.
Compatible with 9- or 10-speed Shimano drivetrains
Not compatible with Dura-Ace 8-speed shifters
Large 11-tooth pulleys with sealed bearing for smooth, quiet running
Dura-Ace 7900 rear derailleur features carbon pulley plates and a wider gear-ratio - yields triple capacity without a GS rear derailleur