Shimano Di2 electronic shifting lets you change from the big to small chainrings, or vice versa, whenever you like while minimizing the risk of a dropped chain. Similarly, you can perform rear shifts without the need to trim the front derailleur to avoid chain rub. Full- and semi-synchronized shifting functions can be selected using the E-TUBE app. With digitally accurate electronic shifts and coordinated communication between shifters and derailleurs, the new Shimano 105 front derailleur offers the best shifting you've ever experienced. Great value, high performance 105 double Di2 front derailleur The Di2 front derailleur's operation is pioneering, smooth shifting is guaranteed thanks to wireless communication with the gear levers. What's more, shifting the rear derailleur automatically trims the front derailleur Full and semi synchronized shifting programable, Synchro shift compatible meaning a single shifter can control both front and rear shifting which can be fully custom tuned to your riding preferences. Semi synchronized shifting means when a front shift is made the rear mech will automatically correct to the appropriate ratio The removal of traditional mechanical cables in favour of electrical wires that connect to the battery not only eliminates poor shifting caused by contaminates, corrosion and stretching, but provides effortless gear shifts Wireless connection to the shifters The front derailleur also trims automatically; the cage moves in response to the position of the rear derailleur on the cassette to ensure no chain rub and a quiet unobtrusive ride, enabling you to concentrate on the road ahead Designed to work with the wider gear pitch spacing Shimano chainsets without sacrificing shifting performance on bikes with 135 / 142 mm O.L.D. Braze-on fit as standard; if your bike does not have a braze-on mount seat tube adapters are available 12-speed E-tube SD300 wire compatible