Shimano SM-JC41 Di2 Junction-B Box

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.

• Frame Junction Box connects via SD50 E-tube wires to four different points: front derailleur, rear derailleur, cockpit junction box and battery mount
• All Di2 components on the bicycle require the same firmware version. Using Di2 components with different firmware versions may cause malfunctions