The whole concept of uni-tubes screams "niche", especially the 16340 Guppy. Niche not in terms of its value or looks, but strictly in terms of purpose.
Look at the facts:
1) It's a 19.5mm diameter, 63mm long, ~50g device.
2) It's super low-voltage-drop, easy to use, but strictly 16340.
The device was designed to be as portable and simple as possible. Compared to a Roller or Dingo in 18350 mode, it feels just tiny.
The tradeoff is that it works with 16340 batteries (strictly original, low-internal-resistance IMR), a form factor few people are familiar with. 16340s are very comparable to 18350s and 14500s, which means that sub-ohm resistances are a bad, bad idea. Some people still use 18350s and 14500s for SLR vaping, but just because they do doesn't mean that they should.
In all other cases, a quality, low-internal-resistance 16340 IMR will
pleasantly vaporise around 1.0-1.5 ml of juice, almost the same as a 18350. (The volt-drop difference between a 18350 AW IMR and its 16340 counterpart is max 0.05V with a 2 Ohm resistance and 0.1V with a 1 Ohm resistance, almost insignificant). Also, the lower capacity of the 16340s/18350s/14500s is not a problem if you carry a couple batteries with you.
So, in the end, the answer is simple:
- If you like mechanical mods for whatever reason other than SLR vaping, and want something easy-to-use, easy-to-carry with loads of performance, then the Guppy is a good candidate if you have something to put on top. It's the kind of mod that you'll throw in your pocket during a night out without getting any weird looks - wives, mums and co-workers actually seem to like it a lot "compared to the other stuff".
There are plenty of sub-20mm atomizers out there that will look great on it, as well as a few 510d type rebuildables that can be used with the Bayou to get a seamless look.
The Diver will work fine with the Bayou, but top-filling it in any tank that has a top/side-refill system might be a bit challenging.
I guess reviews will start to appear soon, but, as usual, you'll get a more objective opinion from people who had it in their hands for a while, or at least from reviewers who share first impressions & experiences over time.
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