Interesting set where you can taste the 4 phases. Bottle A contains the pure new-make spirit. Bottle B shows how the malt develops in a bourbon cask. Bottle C shows how the new make develops in the PX cask, and finally bottle D shows how the finished Dingle single malt is bottled.
A great introduction, for example, at a tasting session with friends, in your whisky club, or of course on your own...