Compatibility: Shimano Di2 drivetrains Recommended Use: wiring Di2 derailleurs to battery Available in three separate lengths for your exact frame needs, the Shimano E-Tube Di2 Y-Split Rooting connects your Di2's battery to the front and rear derailleurs. This E-Tube Y-Split Rooting is compatible with all previous Di2 drivetrain generations, regardless if they're Ultegra or Dura-Ace. To find the right fit for your frame, measure the chainstays first, then the distance from the battery location to the front derailleur. After you find these measurements, find the version that's slightly longer to accommodate your routing needs.