Bowl generally refers to the area where flower or extract is placed to be heated (direct or direct / combustion or vaporization). Bowl is also the reference we use to describe the part of a water pipe that is removed once the user has completed an inhalation cycle. Bowl is also synonymous with Hand Pipe; as in – pass me the bowl, don’t bogart it! The glass bowls are available in a variety of sizes 9mm, 14mm and 19mm.