I have a bong w/ 2 perks and a 18 mm NB bowl. It works fine, but there's no downstem present so it hurts a lot. One of my buddies told me a diffuser would simply do the trick as it would easily attach with the bowl. Another one of my friends said a downstem would attach. My question is if I have the bowl already what actually attaches to it? I understand to some people that this is a trivial question, but please help me out here, because I'm super confused.