Select your style & size:Select options
It’s time to connect.
Shimano’s E-Tube Di2 Junction Box (also known as the B junction) connects all your component and battery wires to make assembly much easier. It's a crucial item along with the five required wire sections to operate your Ultegra 6770, Ultegra 6870, or Dura-Ace 9070 Di2 shift system. The E-Tube Di2 Junction Box is available in two configurations: Internal (SM-JC41) and External (SM-JC40).
- Connects Di2 cycling component and battery wires
- Available in external or internal configurations
- Shimano's Di2 is the most popular electronic drivetrain in the pro ranks
- Item #SHI0394
- Q & A
Gotta Have It
- Familiarity: I've put it through the wringer
It's a necessity!