Snap-on Towel bar bath hook (parametric)

It's a simple hook that snaps on to your bathroom towel bar.  Grip the small inflection point with your thumb to remove (or just push up from the bottom).

I was looking for a hook that wouldn't fall off the towel bar if jostled by (for example) a towel, and so I designed this from scratch (though it was inspired by someone else's open scad hook, but I can no longer find the source). 

The pictures show the 18mm size--this just slightly larger than the diameter of my towel bar.  It's a snug fit on my towel bar--which I like--but it can also work on smaller towel bars without falling off.  A couple other sizes are offered for other towel bar sizes; other parts of the hook's dimensions are unchanged.  Or, edit the 3MF files and modify the clamping radius to match any diameter that meet your needs.

I printed in PETG with 3 perimeters, and I used a brim (though that may be unnecessary).  At my MK4S's 0.25mm “speed” setting, it printed in only 8 minutes.