American whiskey includes both straights and blends. To be called "straight" the whiskey must be one of the "named types" listed in the federal regulations and aged in oak casks for at least two years. The most common of the "named types" are Bourbon, which must be between 51% and 79% (inclusive) corn (maize); rye, which must be at least 51% rye, and corn, which must be at least 80% corn. All straight whiskeys except straight corn whiskey must be aged in new casks that have been charred on their inside surface. American blended whiskeys combine straight whiskey with un-aged whiskey, grain neutral spirits, flavorings and colorings. These definitions are part of U.S. law. Not defined by the law but important in the marketplace is Tennessee whiskey, of which Jack Daniel's is the leading example. It is identical to bourbon in almost every important respect. The most recognizable difference is that Tennessee whiskey is filtered through sugar maple charcoal, giving it a unique flavor and aroma.