RY4 is a very popular e-liquid combining a subtle blend of tobacco, vanilla and caramel flavours. Its an ideal starter liquid, as its not at all harsh and produces a decent amount of vapour.
The somewhat unusual “RY4” designation originates from the company Ruyan (hence the “RY“), but these days numerous variations are produced by different manufacturers all with their own take on the “RY” theme. Incidentally, you may find RY1, RY2, RY3 and RY4 for sale elsewhere which range in delicacy and sweetness, but RY4 is by far the most popular and the best all-rounder in my opinion.
I’ve tried RY4 before, but not Apollo’s version of this classic.