The legal definition of a spirit whiskey is one that is a mixture of neutral spirits and not less than 5% on a proof gallon basis of whiskey. While this category has been defined for some time, the production of spirit whiskey in the United States is a fairly new development. These products are not blended whiskeys (whiskeys of different types), but rather whiskey (aged in charred oak barrels for at least two years) blended with other spirits, such as vodka. Styles vary, with some being clear and others having an amber color. These are primarily meant for cocktails, while a few of the finest artisan examples are ideal served neat or over ice.