I was printing some masks and was planning on sewing the elastic straps together. It was harder than my patience allowed, so I designed these things to snap over a couple of pieces of 1/4" elastic strap. It works really well. I can pry them apart and use them again and again. One could also turn this sideways and fasten a larger size of strap, although I would want to redesign the teeth in the center. I printed in PETG, at .15 settings, with no infill.