Shimano Ultegra RD-6800-SS 11-Speed Short Cage Rear DerailleurShimano's Ultegra Rear Derailleur delivers category defining 11 speed shifting. At the heart of the derailleur is a light, tough, cold forged aluminum body with a wide, rigid pivot design that maximizes shifting speed and equalizes shift effort across the cassette. Smooth spinning pulleys use sealed bearing to keep out the dirt and ensure quiet running in the miles to come. SS (short cage) derailleur is compatible with a 28T max cassette size.