Threaded coupler for 2 liter bottles

This coupler is used to connect two 2 liter bottles for demonstrating a vortex and centripetal force. It has a perfectly snug fit. There are several of these coupler designs out there, but this one is superior to all of them. Want a quick and easy way to score an A+ for your kid's science project? Look no further! We printed a whole plate of these and every kid in class was able to go home with one after the presentation.