@zwol@masto.hackers.town It probably is heat. I'd try IPA somewhere on the inside of the caps to see if it helps. Put some on with a swab, do not rub, let it evaporate, see if it changes texture. Depending on what plastic it is it may melt it a bit, make it flow just for a bit to level, and that would make it smooth. That's also why you don't want to rub it, you’ll mess it up. If you feel particularly adventurous and IPA didn't work you can try a more aggressive solvent like acetone, MEK, or xylol. Or you can just sand them. 5000 grit for shiny, 2000 for matt. Sandpaper available in any hardware store. You can also use nail buffers.