TUN is a term used to refer to a large BARREL or CASK, usually made of wood, used for storing liquids such as wine or beer. It can also be used to refer to a VAT, KEG, or winecask, all of which are containers used to store and transport liquids. A BARREL is a cylindrical container with flat ends, typically made of wood, and is usually around 55 gallons in size. A VAT is a large container, usually made of metal, used for storing liquids. A CASK is a BARREL-shaped container, usually made of wood, used for storing and aging wine or other alcoholic beverages. A KEG is a cylindrical container, usually made of metal, used to store and transport beer. A winecask is a large BARREL-shaped container, usually made of wood, used for storing and aging wine.