At Laphroaig all the spirit that is bottled as either 10 year old or 15 year old is matured in American White Oak Barrels (That contain a nominal 190 bulk litres or 39 gallons) that have been used for the maturation of Bourbon in Kentucky. The flavours that are imparted to the maturing spirit have a slightly "drier" taste than thos imparted from a Sherry cask. Laphroaig has been maturing in Bourbon at least since the 1930s . The bourbon casks also impart colour to the spirit.