Bezel to neaten the appearance of the meter and add a little protection to the seam between the base and lens.  Inspired by a similar bezel I saw photos of online but created from scratch.  The mA meter I have measures 45MMx45MM, if yours is larger or smaller you may need to adapt the model or stretch in your slicer.  The bezel in the photos has some print quality issues, was made with leftover filament that's been sitting open for over a year on a printer I'm still tuning.  It's good enough for the job it needs to do.