My favorite is your Black Label Ry4 Day and Night. I bought some to take with me on a business trip. Put it in a DCT and went
through nearly the whole bottle in 2 days. I only had 10 ml so I had to stop and save some for dripping so it would last longer. It is hard to describe what makes it different from the regular Ry4 but I like it better. It is maybe more buttery or caramely. I live in Houston and it was really nice to place an order one day and it be in my mailbox the next by regular mail!