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E-Tube Di2 Junction Box

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Current price: $25.99 - $28.04 Original price: $32.99
Up to 21% off

Style & Size:

Size Chart


Where the wires converge.

The E-Tube Di2 Junction Box is what is referred to as the B Junction. This is the point in the wiring system where all the component pieces converge. 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). The Internal style is designed to be located inside the bike frame (usually inside the down tube, tucked in from a hollow bottom bracket shell). The External version is designed to be fixed on the outside of the bottom bracket shell, usually fastened to the cable guide.


  • 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
Crankset Compatibility
2 x 10
Compatible Components
Shimano Ultegra Di2
Recommended Use
ditching your mechanical tethers
Manufacturer Warranty
2 years