This Dura-Ace 9000 series 11-speed mechanical rear derailleur features Shimano's most refined mechanical design to date. Shimano Dura-Ace derailluers have also been known as a benchmark for clear, crisp and accurate shifting. The RD-9000 takes shifting quality to the next level with new pivot points that provide a lighter action or more clearly, less shifting force needed from your hands at the shift lever - Shimano claims a whopping 47% less shifting effort. Shifting effort is also more equal through the entire cassette for the same feel whatever cog your are in and the distance required to move the shift lever to change gears has been shortened.
Some of the more notable details of the Dura-Ace 9000 rear derailleur include a carbon fiber cage that mitigates road vibration somewhat and helps reduce the weight a few grams over the 7900 series. The RD-9000 has a low profile cable pinch bolt which has been repositioned for better leverage reducing shift lever pressure. For the best shiting performance, Make sure you use Shimano's 11-speed specific low-friction derailleur cableset included with the shift levers.
For 11-speed mechanical systems only. Maximum largest rear cog 28t