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Shimano E-Tube Di2 Junction Box
ShimanoE-Tube Di2 Junction Box

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
  • Reviews
  • Q & A

A box with plugs

  • Familiarity: I've put it through the wringer

Just try and use your Di2 system without it, I dare you.

Works well.

  • Familiarity: I've put it through the wringer

Works great, make sure to plug any unused ports (like in 1x setups) with the shimano di2 port plugs, or else water will get in and short it out.

Gotta Have It

  • Familiarity: I've put it through the wringer

It's a necessity!