E-Tube wires are used for Dura-Ace 9070 11-speed, Ultegra 6870 11-speed and Ultegra 6770 10-speed. A Di2 system requires six connecting wires (4 for Ultegra 10-speed).
The shortest wires in the 250mm-400mm rage connect the junction box to an external battery and lower junction box to the front derailleur. One quick note: an external junction box is under the bottom bracket while an internal is generally inside the lower portion of the downtube near the bottom bracket. Wires in the 500mm-600mm range connect the lower junction to the rear derailleur while wires in the 650mm to 1000mm range connect the lower junction box to the junction near the handlebar area. For 11-speed systems, you also need two typically 400mm wires from the levers to the front junction. We obviously suggest measuring for the exact lengths when possible.
E-Tube Di2 wire represent an improvement over first generation Dura-Ace Di2 wires because E-Tube use smaller 2 core wires instead of the 4 core used on first generation Dura-Ace. E-Tube wires are compatible for both internal and external routing so there is no need to buy separate internal or external wires. The E-Tube Di2 wires are lighter with smaller connections so there are smaller holes required in the frame for internal routing. Connections on the E-Tube system are water tight without the requirement to install a shrink wrap seal like on 10-speed 7970 Dura-Ace Di2.
E-Tube wires are not compatible with 10-speed 7970 Dura-Ace Di2 components