Mask Adjustment Clip

My kids need their masks adjusted for school. We've been adjusting them by tying a knot, but this is difficult to adjust correctly. So I designed these clips which will slide until you clamp them shut (they have teeth to stay in place). They're small and only take a few minutes to print. I've included one version with a loop to help prevent it from falling off if it gets loose and another version without the loop.

I've been making these out of PETG, but I'm assuming other materials will work just as well. Some flex is required. Unfortunately I wasn't able to design a good loop version without supports, but you shouldn't need much support at all.