I don't know if they are plastic; thought the replacement white ones were actually nylon or something of the sort, 'tougher' and not brittle... ? Regardless, I don't bother resetting my trip odo anyway, no real need to. I'm happy enough to have done the replacement (gear bought here from the host) without any problems, so I reckon it's best to leave sleeping dogs lie.
Guaranteed 'not to break'? A
car part? 0_0