Shimano Ultegra Junction B Internal Wire Routing 4-Port

SHIMANO – Junction B – E-TUBE – Internal DI2 Wire Routing – 4-Port

For internal DI2 wire routing, SHIMANO’s SM-JC41 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-JC41 junction, which is housed inside the bike frame.