Electric Wire / e-Tube cable
The Shimano EW-SD50 electric wire connects the individual parts of the Di2 system to each other. They're available in a bunch of different sizes. You'll need about 6 of them, depending on your specific setup and frame size. The generally available sizes are:
That 1600mm wire is meant to be used on E-Bikes only, but I haven't seen it fail on road bikes myself. If you're thinking of using this on a road bike - you probably can.
You can connect EW-SD50 wires to the next generation EW-SD300 E-Tube wires using the EW-AD305 adapter. This is good news, because that means you can use all of your older components with future Di2 series.
An EW-SD50 wire's diameter is 2mm. However, the plug - or connector - itself measures 4.5 - 5mm in diameter. This means that the plug doesn't fit through frame internal cable stops found on many older frames. This is something to keep in mind when converting older bikes to (wired) Di2.
Details & Specifications
|Shimano model number:||EW-SD50|
|E-Tube Port type:||SD50|
|Component series:||Non-series components NON (All)|