Hookah has three common types of bowls used to place shisha into: standard bowls, funnel bowls, and inverted bowls. Bowls are usually made with clay or ceramic, and they must be retardant due to the heat from the coals.
A standard hookah bowl is circular with an crater-shaped indent on the middle of the bowl. There are holes located on the bottom of the crater, and this is where the smoke from the shisha is pulled through. A cover or a piece of tin foil must be used over the bowl to place the coals on top to heat the shisha. Standard bowls are fairly cheap in comparison to other bowls, but they can burn a bowl the quickest because of how the bowl is structured.
A funnel bowl is also circular and shaped like a standard bowl, except there is only a single hole located in the center with it being raised all the way to the top of the bowl. This allows for shisha to be packed on the sides of the funnel bowl and the smoke to be pulled through the center of the bowl. The funnel shape allows for the bowl to support more coals and prevent the shisha from burning. However, the hole where the smoke is pulled through can be blocked by tin foil if it is not secured onto the bowl. Funnel bowls are the most common type of bowl used.
An inverted bowl is an uncommon type of bowl that is the most proficient smoking bowl, but it is also the most expensive. The shisha is put into a detatchable bowl above the area for the coals. The bowl is spun above the coals, and the shisha is heated by the heat from the coals rising to the bowl. The lack of direct heat causes the bowl to heat up slower in comparison to other bowls, but there is no health risk from the coals because they are not directly attached to the bowl. A picture of a hookah with an inverted bowl can be found on the anatomy page.