dude 2 liters are nothing. weakest kind of gravity bong. i use a simplay orange oragne juice bottle. they work best....the opening at the top or more than twice the size of a 2 liter....fast clears. a lot of you will puke the first time you get a nice pull. hahahahaha yeah gravity bongs and my roor are the only things that i can make myself cough on...but i can still get some nice ass rips without coughing. im p.r.o. bitches!