There are various styles of bowls that are compatible with many different water pipes and downstems. Replacement bowls and downstems are relatively inexpensive and can be easily replaced if they are lost or broken.
A downstem is a tube-like device which fits directly into a water pipe, with one end submerged in water. Without this, a glass pipe would be little more than a chamber with holes. A bowl then fits onto the top of the downstem, providing somewhere for you to burn your herbs.
We currently stock 14mm, 18mm and 19mm glass bowls and downstems, and our selection will expand in the near future.