My wife is a science teacher who teaches teachers how to teach science. While preparing a biology lesson for elementary teachers (see photo) she realized that she had misplaced the cap of her bottle. Being resourceful she simply covered it with plastic wrap and a rubber band.

But I have a 3D printer! So I downloaded CreativeTool's most excellent bottle cap and printed one out for her. Problem solved.

She was so impressed that she asked me to print another one and drill a hole in it to act as a drain. (see bottom cap in picture)

But I have a 3D printer! So I simply uploaded the cap into Tinkercad, booleaned a hole into it, and printed one out for her. Problem solved. That's what you have here.

This really impressed her.

So she asked me if I could print 20 sets for her students.

Well, I do have a 3D printer…