These are on the front of the Retro-Raygun and are the only part (aside from the turned acrylic emitter) to get a non-metallic treatment. These can be made in polished plastic or painted with gloss enamel.
This was printed on a Type A machine with suspect tolerance. It may require minor dimensional adjustment to provide properly assembly clearance.
Originally done in pink PLA, sanded smooth and given a coat of clear gloss.