Shimano did it right when it came to designing the new Ultegra Di2 wiring setup. It's slimmer and has smaller connectors than the Dura-Ace Di2 system, giving your bike a cleaner look with less messy wiring. You can also run the Ultegra Di2 wires internally or externally, as long as your frame is compatible with internal wire routing. This front wire harness is waterproof and easy to install with the new junction box design. Just plug it up and hit the road.
This wire harness connects your Ultegra Di2 Dual Control Levers to each other, and has an input for a wire that connects both Levers to the junction box
Compatible with internal or external Ultegra Di2 setups
Ultegra Di2 System requires 1 Handlebar Wire Harness and 4 Wires (Available in 13 different lengths under Nashbar item #SH-SD50S, SH-SD50M, SH-SD50L, SH-SD50XL): 1 wire from the junction box to front derailleur, 1 from the junction box to rear derailleur, 1 from the junction box to battery, 1 from the junction box to handlebar wire harness