Take it to the cleaners.
Providing for a clean aesthetic that allows any bike to look like a Tour-crushing superbike, the Shimano EW-RS910 is a Junction A box for internal handlebar ends or dedicated frame mounts. Connecting the various components and odds-and-ends of the Shimano Di2 drivetrain, the EW-RS910 also makes for a convenient charging port for your Di2 drivetrain.
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Mfg PartNum: IEWRS910
Shimano EW-RS910 Junction A for Internal Bar/Frame Mount; Its a must have for the Di2 system. It fits in the handle bar or specific placement on bike (down tube). Engineering, I wish it was more user ergonomic; the button is 'stiff', and the door opens downward to 'charge' the proprietary Di2 system battery....however, you still need this to complete the system. Allows user to plug into PC update components, and charge battery.
I wanted to clean up my front end and this did the trick. It should become the standard approach - more aero for sure.
It just works. I also upgraded to bluetooth at the same time...