One of the most common varieties is the ice bong, which is a sub variety of a slide or carburetor bong. These are typically made of glass or acrylic, like the one to the left. Ice is placed in a twist or ice trap in the neck. This has the effect of cooling the smoke when the user comes to inhaling. These bongs are typically bright colors and are popular due to the durability, ease of use, and controllability. They usually have carburetor holes on the opposite side to the bowl or slightly to the left or right of that position. These tend to have larger chambers than other bong varieties, as ice is used rarely in smaller bongs.

Bongs of more expensive design can sometimes feature ice catchers, which allow ice to be stored in the main chamber where smoke resides. This ice can cool the smoke to below room temperature, sometimes allowing smokers to intake significantly more smoke and hold it in the lungs for a longer duration.

From Wikipedia.