so in my college ceramics class i made a bong, and i read online that the stem hole's either 18mm or 14mm so i made the hole in the base a little under 2cm,but just found out that it meant the hole in the stems 14 or 18mm.......anyone know how i can fix it? the bowl my friend gave me is 14mm but the holes around 18-20 and i don't really wanna buy a new one. thanks for any help