Whistlepig Aged 18 Years Straight Rye Whiskey W/ Whistlepig Bottle Stopper. A long and patiently aged whiskey is only as good as the grain it's born from. With our oldest expression to date, we’re tapping into the time-honored techniques of the farmer distillers who invented the category in America's early days. Our mash bill 79% rye, 15% malted rye and 6% malted barley creates a sipping experience that evolves on the palate from soft and supple to rich and savory. A thrilling encounter accentuated by 18 years of maturation in virgin oak.