Everything you need.
This Shimano E-Tube Di2 Complete Wire/Power Kit is a complete kit and contains all the necessary parts to hook up your Ultegra 6770 Di2 electronic components. You'll get five wire sections — front wire harness, down tube, front derailleur, rear derailleur, and battery. The front wire harness has an integrated A junction, but the B junction is a separate unit. You'll get that as well. The kit also includes a battery and battery mount along with a charger and cable.
We have the E-Tube Di2 Complete Wire/Power Kit in a number of wire length options to fit differently sized frames. You can also choose between the internal or external battery mount. For bikes designed to accept it, the Internal kit will route the wires, B Junction, and battery inside the frame tubes. Conversely, the External kit routes all the wires and battery externally.