A keg is a cylindrical container typically used to store and transport beverages, especially beer. Kegs come in various sizes, with the most common being the half-barrel, which holds about 15.5 gallons. They are made from stainless steel or aluminum, which helps preserve the quality of the drink inside. Kegs are designed to be pressurized, allowing for easy dispensing of the beverage through a tap system. This makes them popular for parties, bars, and events. Additionally, kegs can be reused and recycled, making them a more sustainable option compared to single-use containers.