See, the plastic bag you pull out as you light it, and it fills the bottle with smoke. Then you take the lid off and clear the bottle and as you suck the smoke out it sucks the bag back inside the bottle and you're ready to go again It acts like the water does in a gravity bong. (Gravity bong = bottle with no bottom you push almost all the way down into water. Then you light it as you lift it out of the water and the water sucks the smoke into the bottle. Then you take the lid off and push the bottle down into the water as you hit it and you WILL be fucked up.)