This is a cap for a "one use" eye drop container, customized for the Systane brand. Their vials have a slight bump at the tip, and this cap "snaps" over that bump.

I get 4-5 uses out of a "single-use" vial, but to do that, I need to keep the tip covered, both to avoid contamination (one-use eye drops do not contain preservative) and to stop evaporation.

To keep the vial upright between uses, I cut a slot in the cardboard box that contains the eyedrops and simply drop the vial into that slot. It works great.

I have provided the parameter-driven Fusion 360 file, should you want to make changes to the design. Just enter your own dimensions, save the STL file, and print.