Eyedropper aiming device. The elliptical ring fits around your eye, the other end accepts the sort of eyedrop containers that I got after my cataract surgery (I assume they're pretty standard size containers). It's a useful tool for holding the eyedropper tip vertically about ½" from your eye i.e. not too close to contact your eyeball (but check this before you use it!) and not too far that your aim has to be superhuman. I've printed this in PET-G and ASA (pictured) at varying resolutions, and given out a bunch as gifts for no apparent reason.