Drums and tanks, although similar in purpose, have several defining differences. Tanks are man-made containing utilities, suited for storing liquids. They have no specialized size and shape requirements, and come in spherical or rectangular shapes, sizing from small (can be held in a hand) to very large (several dozens of feet). Tank commonly have no pressurization. Drums, on the other hand, come in specified sizes, and are typically barrel-shaped metal containers. They are often specifically designed for storing dangerous goods, and are sealed (closed) under high-pressure.