Shimano Ultegra Di2 RD-6870 11 Speed Rear Derailleur
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 gear. Programmed automatic motion at the touch of a switch makes this derailleur quick, smooth and effortless to shift. The removal of traditional mechanical cables in favour of electrical wires not only eliminates poor shifting caused by contaminates, corrosion and stretching, but provides effortless gear shifts. Derailleur contains a saver (fuse) function, where the inner structure is protected from strong impacts.