I have one. It is indeed leak-proof (kicks around in my backpack pocket with my Crown and Atlantis tank, none of them leak!).
It has good airflow for it's design, not too much and not too little (using the 0.5ohm coil), and it's hidden, giving it a nice look. It's easy to fill (albeit messy), you just gotta be sure to let the excess juice run off the coil before taking it out, or else it'll drip everywhere.
The coils themselves perform pretty well, but the flavor isn't overwhelming so I stick with more menthol-ish flavors, or flavors with a sharper taste to them (something citrus-y). They also come with a mesh guard on the top of the coil-head to prevent debris from gunking up the coils.
The tank comes in numerous colors (which is a plus for some people), and with the giant glass cup, it's easy to see when it needs a refill. Plus it comes with 2 DT (One to match the tank, and a clear one).
All in all, a decent tank to kick around.
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