Hell I still make gravity bongs out of a 5 gallon bucket filled with water, a 2 liter bottle, a socket, and electrical tape if need be. Heat the very middle of the 2 liter bottle cap with a lighter, then make a small hole with a knife or something and just push the socket in. It should make a pretty airtight seal on its own but if need be add tape. Keep in mind a smaller socket is best so the cap can still screw onto the bottle tightly and not be out of shape. Add a screen if desired and cut the very bottom of the 2 liter bottle. VOILA! A gravity bong lol