Since the Quad-Flex actually is a Nautilus X, performance in that configuration is predictably good for MTL vapers who want maximum flavor in a low-power tank. Happily, performance is also satisfactory as either an RDA or RDTA.
That’s the good news. The bad news is that, unlike my other Genny-style RDTAs, the Quad-Flex has no fill port. To fill the tank, the top half of the tank (with the deck and the wicks hanging down into the reservoir) has to be unscrewed from the glass reservoir section on the base. Without taking care, that can be messy. In fairness, the same can be said for every fill method, but the Quad-Flex RDTA requires a bit more carefulness than some.
The big question about the Quad-Flex is: Who is this product for? Yes, it’s clever enough, but how many vapers will actually want to use it in more than one configuration? I’d guess some, but not too many. My hunch is that relatively few vapers go back and forth from direct-lung to mouth-to-lung vaping.