Essentially, a bain marie is a pot inside another pot containing heated water. These are used for keeping a variety of pre-cooked food warm for a period of service time. The benefit of wet well bain maries is that the water eliminates the food being kep warm from sticking to the base of the container. Dry well bain maries do not use water. Instead, the pots are located above the element. Not as popular as the wet well bain marie, they still have their uses. The gastronorm sized machines can take a variety of combinations of gastronorm containers.