A barrel is a cylindrical container, often made of wood, that is used for storing and aging liquids like wine, whiskey, and oil, as well as other goods. It can also refer to a specific unit of volume, especially for oil. Modern barrels are also made from materials like plastic and stainless steel, and are sometimes used in a more general sense as a synonym for "drum" when referring to a cylindrical shipping container. Container and its uses Liquid storage: Barrels are traditionally used to store liquids such as wine, whiskey, and oil. Aging: Wooden barrels, especially those made of oak, are used to age beverages like wine and spirits, which can add flavor and complexity. Transport: Barrels are a type of shipping container for various bulk goods, including liquids and powders. Material: While wood is traditional, modern barrels can be made from other materials like steel, plastic (like HDPE), and stainless steel. Other uses: The term "barrel" can also describe other objects shaped like a barrel, such as the tube of a firearm or the drum of a watch. Unit of measurement Varying capacities: A barrel can be a unit of capacity with different volumes depending on its use. Oil barrels: The most common volume for an oil barrel is 42 US gallons (about 159 liters). Other barrels: Other barrels can have different capacities, such as the US beer barrel (117.3 liters) or the UK beer barrel (163.7 liters).