Unlike Bourbon or Rye, which, by definition, must be aged in new oak barrels, Michter's US1 Unblended American Whiskey is aged in a way that utilizes whiskey-soaked barrels to achieve a rich and unique flavor profile. In late 2013, then Master Distiller Willie Pratt agreed to re-release US1 Unblended American Whiskey after a nearly three-year absence from the market, deeming it "just right" and "the best it's ever been." Crucially, Michter's US1 Unblended American Whiskey never contains grain neutral spirits – hence its "unblended" distinction.