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Shimano E-Tube Di2 Junction Box

Sale $20.95 $29.95 30% off

Item # SHI0394

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  • One Color, External/SM-JC40 ($20.95)
  • One Color, Internal/SM-JC41 ($20.95)
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Item # SHI0394

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-JC40) and External (SM-JC41). 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 all your component and battery wires
  • Available in two configurations: Internal (SM-JC40) and External (SM-JC41)

Tech Specs

Crankset Compatibility:
2 x 10
Compatible Components:
Shimano Ultegra Di2
Recommended Use:
ditching your mechanical tethers

Size chart

Fuji Bicycles


Geometry Chart


Altamira LTD

Seat Tube


Effective Top Tube








Head Tube


Head Tube Angle


Seat Tube Angle


Bottom Bracket Drop


Chainstay Length



44 44.0cm 51.5cm


36.3cm 72.1cm


72.0 deg 75.0 deg 6.9cm 40.5cm 97.1cm
47 47.0cm 53.0cm


37.0cm 74.1cm 13.0cm 72.5 deg 74.5 deg 6.9cm 40.5cm 97.7cm
50 50.0cm 54.5cm 54.0cm 37.0cm 76.0cm 14.0cm 73.0 deg 73.5 deg 6.9cm 40.5cm 97.6cm
53 53.0cm 56.0cm 56.0cm 37.9cm 78.3cm 16.0cm 73.5 deg 73.5 deg 6.9cm 40.5cm 98.6cm
55 55.0cm 57.5cm 58.0cm 38.9cm 80.1cm 18.0cm 73.5 deg 73.5 deg 6.9cm 40.5cm 100.1cm
58 58.0cm 59.0cm 60.1cm 39.7cm 82.1cm 20.0cm 74.0 deg 73.5 deg 6.9cm 40.5cm


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