Shimano Di2 Sm-Jc40 Junction

SHIMANO Junction B External Wire Routing 4-Port SM-JC40

SHIMANO - Junction B - E-TUBE - External Wire Routing - 4-Port
For external DI2 wire routing, SHIMANO's SM-JC40 Junction B is the central connector for DI2 systems. Wires from the front and rear derailleurs, cockpit area, and battery all plug into the 4-port SM-JC40 junction, which is mounted under the bottom bracket.