Cognac is a type of brandy produced in the area around the town of Cognac in south west France. The spirit must be distilled twice in copper pot stills, and matured in French oak casks for a minimum of two years. Cognac is often labelled as VS, VSOP, or XO, which are official grades that refer to the length of maturation, and there are also vintage Cognacs from particular years. Big names such as Hennessy, Courvoisier, Remy Martin and Martell dominate the market, but there are several reputable smaller producers.