Koval Four Grain is an American whiskey-style spirit made from a mashbill that uses four grains rather than focusing on just one or two. Bottlings at 47% ABV tend to show a fuller, more robust character than lower-strength releases.
The "Single Cask" label means the spirit comes from one individual barrel instead of being blended from many casks. That can make each bottling a little different, which is part of the appeal for drinkers who enjoy more distinctive small-batch releases.