as far as i know there are two common sizes 14.5 or 18.8 but if you are getting the down tube from a headshop just ask them first what it is
brad1028 Reviewed by brad1028 on . Bong slide hole diameter So I just made a bong in pottery and would like to drill the hole in it for a slide, but I need to know what size hole to drill. Is there a standard slide diameter? Or should I just buy a slide first and figure it out from there? Rating: 5