Shimano Ultegra Di2 Junction Box Parts Electronic Shifting Parts

Shimano Ultegra Di2 Junction Box. As an improvement over the Dura Ace Di2 setup, the Ultegra Di2 group uses a junction box to simplify the wiring, giving you a cleaner look with easier setup. The junction box mounts under your bottom bracket shell for external wiring and connects the wires coming from the derailleurs, levers and battery.