i made a gravity bong the other day with a 1-liter gatorade bottle, a 2-liter soda bottle, and the bowl from my metal pipe. first gravity bong i've ever tried, actually, and i was already pretty stoned when i made it so i only had 2 hits off it. but... i just woke up. so i think i'm going to wake and bake with it. this should be fun.