Now simplified with a single derailleur cage length, the new 12-speed Shimano Ultegra R8150 rear derailleur packs our fastest, most precise shifting into a more approachable option. With our fastest, most accurate shifting, the new 12-speed Ultegra R8150 rear derailleur is more versatile than ever thanks to a single cage length option that is compatible with 28-34T low sprockets.Ultegra Shadow design with Di2 technology, shifting is easy and precise - just a light touch, as soft as a mouse click, is sufficient for the front or rear derailleur to instantaneously select the correct gearThe rear derailleur is now the brains of the system with wireless connectivity to the shifters. It acts as the point the system is charged, provides ANT+ connection to 3rd party devises and replaces the handlebar junctionButton on the derailleur for Di2 operations, and LED light denotes synchronized shift mode, setting mode and charge requirementsSleek appearance with low profile Shadow design construction