Have you had the threads on the molded plastic bezels of your A/C gauge set crack?
You can find replacements for most gauges, but not all, particularly if they are older.
And you may have a problem matching up what is available to your particular set.
But the biggest problem is that the new ones will just break again.

On my trusty gauge set I had them taped in place for a long time and finally decided to do something about it.
I trimmed off the cracked edges leaving just the windows.
Then I designed and printed these rings and placed the original windows into them.
The results are as shown.

I could also have replaced them with 2.5" diameter glass or plastic disks.

You can scale these to fit your particular gauges in your slicer, and it might be a good idea to print up to the first threads and stop for a test fit.
If your gauge set has shallower threaded portions on the bezels you can also print up to the height you need and stop printing, assuming you print with the front ring against the print platen.
If you try to scale it in the Z direction you will affect the thread pitch, so I would not suggest doing that.

I printed these in ABS because it stays somewhat flexible.
If printed in PLA they would be OK too.

I hope they work for you. :-)