Evan Williams Single Barrel is between nine and ten years old (since each bottle of the bourbon is matured in a single cask rather than being blended together from a batch of casks, each bottle's exact age varies). In addition, the barrels used in this release were matured on the top floor of Rickhouse Y in Bardstown, Kentucky. Since the top floor of the distillery's warehouse is exposed to more heat than other floors, the bourbon and oak are forced to expand and contract as the temperature gradient changes."