Although keg sizes are not standardized, a typical U.S. keg holds 15.5 gallons, or 1,984 fluid ounces. In the United States, a keg is equal to a half barrel. There are also pony kegs, which are equal to a quarter of a barrel.
Some brewers manufacture 5-liter mini-kegs that are not refillable. Typically, kegs are made out of stainless steel; however, they can sometimes be made of aluminum. The keg must be in an upright position with the opening on top for the beer to be dispensed. Kegs can be tapped either with a party pump or a gas tap.