The Shimano Dura-Ace RD-9000 rear derailleur is, quite simply, one of the absolute best rear derailleurs you will find on the market today. To give you top performance, Shimano has redesigned the Dura-Ace rear derailleur to give you a lighter operation. What this means is that you'll have more even shifting at both ends of the cassette which makes your shifting smoother and quicker. By crafting the Dura-Ace RD-9000 out of carbon fiber and forged aluminum, Shimano has made a derailleur that is light, stiff and durable so you'll get fast and precise shifting mile after mile. Shimano has also made the Dura-Ace RD-9000 able to handle sprockets up to 28 teeth in size to give you more options with your cassette. The Shimano Dura-Ace RD-9000 rear derailleur is an 11 speed rear derailleur.