I found an awesome decorative bottle at hobby lobby and turned it into a bong! (Sorry, no pics as of yet). I took out all the decorative peppers that were in it, washed it out, used a 5/8 diamond drill bit to make the hole, stuck a down stem in, and smoked that muh fuh. Now I want to upgrade it and put a diffused down stem in and that's where I need some help from my fellow ents... The hole for the down stem is 5/8 and all of the diffused down stems I've seen are measured in mm. So what size would I need? *If necessary I can drill a bigger hole Thanks!
well that would be 15.875mm to be exact, I would get a 14mm stem with a rubber gromet to keep it sealed.