Shimano Dura-Ace 7970-Di2 SM-EC79 diagnostics tool

There’s nothing quite like a drivetrain that utilizes a $400+ dollar diagnostic tool.

Shimano Dura-Ace 7970-Di2 SM-EC79 diagnostics tool | eBay

First look of that I thought it was the battery charger…

We buy an allen key, rich Fred buys this instead…