Not sure if there were multiple revisions of the Micro, but my original battery had a white paper casing and the connector was a slightly different shape. Nothing a little wire cutting and soldering couldn't fix though. Battery is in perfect condition otherwise!

Great replacement!

I got a GameBoy Micro dirt cheap as it would not turn on. The blue lights flashed when you plug it in, but nothing else. So I researched, and the first option I got was "dead battery". I rolled the dice and ordered one up from the good folks at Handheld Legend.
The only difficult part of the process was getting the battery plug to sit in the port. I had to use a tiny plastic stick to push it into place. Fired it up and like magic, I was back in business. Very happy so far.

It was very difficult to get the battery to fit, bit I eventually was able to make it fit. it's okay so far! You may struggle to make it fit.