The Shimano 1st Gen E-Tube Di2 Wire plays an integral and important role in assembling your 6770, 6870, or 9070 Di2 group. Without it, you can't install your Di2 derailleurs, shifters, or battery. So, check the size chart on this page for length, and don't worry about the rest. If you're running Ultegra 6770 or 6870, or Dura-Ace 9070, this E-Tube Di2 Wire will connect up all the moving parts. Its connectors are the same, regardless of application, so all you have to do is choose the length that's best suited.