A barrel is a container for wine, beer or spirits and some foods such as salted herrings and olives, originally made of curved slats of wood bound with iron hoops. The wood often imparted specific flavour to the contents of the barrel, especially if they were selectively aged in that wood. Now they may be made of steel or other materials. It is also a liquid measure equivalent to 35 imperial gallons (159 litres, 42 US gallons).