Ever wonder what makes a single barrel whiskey just that? Single barrel whiskey (or single cask whisky) is not just limited to whiskey/whiskey. Each bottle of Single Barrel Whiskey comes from an individual barrel that it is aged in and may have some variation from barrel to barrel. This also makes each one a little more rare and limited and the bottles are often hand numbered. Single Barrel Spirits may age uniquely barrel by barrel because no two barrels are the same. When you want to move up from your usual bottle of booze, try the single barrel next.