Update March 2025: I've updated the model description after some confusion and added a button top version.

The flat top profile was tested to fit flat head batteries from Liitokala and Sofirn. This should fit almost all brands with flat tops.

The Button top profile is slightly taller. Please report back as I don't own any non flat-top batteries.

You can check the dual-battery version if that's all what you are looking for.