First impression: I think this is what you would expect from another 4-ish? years on the regular single barrel. There's naturally a lot of similarity - same flavors are there, with fruit, vanilla, toasted brown sugar, but richer, smoother, and definitely more oak than the regular single barrel. I really like it, although wonder if this may be pushing the limit for aging this whiskey before it becomes too oaked. Quite a bit less alcohol burn despite slightly higher proof. Seems worth the 15$ premium over the regular single barrel. I really like the SiB, but this is even better. Update: this is really delicious. After having a nip of this alongside the regular SiB, this is a more significant upgrade than I initially thought. Update 2: having tried quite a few barrel proof bourbons in the six months since opening this, including some greats in JDSBBP, Stagg Jr., and Garrison Cowboy and Balmo, I prefer this to all of them (although Cowboy is fairly close). The complexity, depth, and richness is superb. 5 star whiskey.