I bought one and I assume you mean this?
$12.79 DBOX PuriTank Bottom Coil Glassomizer (3.5mL) - 2.4
It appears to be the real deal due to the box, the listed parts and the documentation.
I was running it on an eGo-C Twist and everything worked fine for about 2 days. Then the
threads on the 510 connection on the Puritank base pretty much destroyed themselves. I now have a base I need to replace (yeah, only $2 but still).
I took a close look at the base connection and it appears to have a very light chrome coating over what I can only call pot metal (!). About a third of the connector has literally broken off (think of slicing a third of a cake away). Completely worthless at this point and no, I was and am not ham handed. I completely understand how to
thread a connector
Bottom line? I will be a lot more cautious next time