I'd really use ABS or ASA for these. PLA ones may hold up ok, and PETG is probably fine, but they are mechanical parts and need to be strong so I would just say ABS is a good plan.

Designed to print as it is without supports. You're welcome. Oh, turn on your fan, real high. Even if it is ABS. That helps.

The diameter of the peg is slightly under 6mm. That's what my shelf wanted. If you want some other peg size, message me and I'll post a new one. I'm friendly like that.