Sprinkler Riser, 1/2" Stopper

This is a remix of https://www.thingiverse.com/thing:2837481 that is basically just a cap/plug for a sprinkler riser.

Interestingly the default size is so exact (and therefore tight) that it doesn't really fit properly. I had luck printing the whole thing at 106% size though you may have to play with it a bit to get it right for your case.

The preview looks kind of funky, but it prints like the sample photos.