What is a glass down stem?
Glass bongs either have a stem or are stemless. A lot of bongs such as glass beaker bongs use a down stem and a glass cone piece.
The down stem goes into the bong and the cone piece goes into the stem.
Above is a diagram of how a down stem fits into a glass bong and then the cone piece fits into the stem.
This is a typical and by far the most common example of a how an all glass bong with down stem operates.
There are other types of glass stem such as 18-18 or 14-14, but these are far less common with the exception of some German made bongs.
All of the beaker bongs we sell (unless stated) have an 18mm female joint and fit an 18-14mm glass down stem just like in the picture above.
Here is a diagram of a typical down stem.
The diagram above also shows how the stem is measured. The correct measurement includes the tapered glass joint. This makes it easier to measure and fit a glass stem.