..less smoke and more of a vaporizer type action if you have it on when smoking...also for keeping seeds from popping everywhere...or maybe so you can get stoned and then say hey! whats this for?
ok well if you smoke the bowl with the cap on it makes the weed burn slower, uh you get high because of it. And so you can pack a bowl then throw it in your pocket. I can't belive you didn't know whut a cap was for.... oh well.
yeah, if youre talking about what I think your talking about then its just what overgrowray said, it restricts air flow so bowls burn slower and last longer, its also convenient for taking a bowl on the go.....But if youre not talking about what I thought you were talking about, then its just there to fuck with your head...
That little cap keeps the smoke in. just put your thumb over the hole, pass it, cough, breathe, whatevre and the smoke waits until the next hit.