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Your cart is empty.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).
Carlos Ostos
September 5, 2025
It is an expensive item for its size but essential to install Di2
heathtx
September 5, 2025
If you are going to run your Di2 cables inside the frame tues, this is the part you want. The picture is of the external mount box, but the internal box is the one I received. Just remove your crank, plug in your 4 wires, tuck this back into the frame tube, reinstall the protector sleeve and crank and you are all set. A very clean install of shifting perfection!!
Cornel
August 30, 2025
I decided to build my new road bike with Di2 electronics. I didn't want to drop $1,500 at one time on the kit so I bought one component at a time. It all came together nicely and all components work fine. I highly recommend this product.
tbstk
July 31, 2025
Works great
Ramil Basco
July 25, 2025
Wow this thing is so light and tiny! It does it's job, nothing fancy.Good seller...
Francisco Lima
May 12, 2025
Gracias
ShopLocalNotHere
May 2, 2025
perfect
fuel98rider
February 11, 2025
Not much to say about this junction box. It’s a necessary part for installs. This allows you to easily stuff it in the seat tube or down tube to conceal it. I added foam insulation around the ends to make it quieter inside the tubes.
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