Shimano SM-JC41 Di2 Junction Box

For internal DI2 wire routing, SHIMANO's SM-JC41 Junction B is the central connector for DI2 systems.

and battery all plug into the 4-port SM-JC41 junction, cockpit area, which is housed inside the bike frame., Wires from the front and rear derailleurs

Mfr Claimed Weight:4.1g

For internal wire routing