Somehow, Di2 can't help but keep getting smarter. With a new Bluetooth battery and Shimano's E-Tube Wireless app, you can now change your shifting preferences wirelessly in the middle of a ride with a smartphone or ANT+ head unit. New versions of Deore XT Di2 will ship with this compatibility built-in, but Shimano created the BM-DN100 Di2 Battery Mount to allow current Di2 users to adapt their earlier generation Di2 drivetrains to work wirelessly as well. If you have your drivetrain set up externally, you'll need this mount, as well as a compatible wireless unit or display to go wireless.