With glass bongs giving the option to later make modifications such as larger bowls for your herb, or an addition water chamber that slots on to your bong (known as a bong precooler). These will take your smoking level to a whole new level of coolness. Adding a precooler to your bong is basically like having 2 bongs. It is a glass chamber that you fill with water, the same way you would do your bong, then you take your bowl out and insert the precooler. It can seem confusing at first but once you have it in front of you it is very simple. I have a few of these myself as they are easily removed and replaced, it keeps my smoking sessions fun and refreshing, not to mention the smoke is made even purer!