These are not all created equal.
If you pop the cap and look at the wire inside the carto, you'll have either a bare/copper wire showing, or a green coated/wrapped wire showing. The cartos with the green coating/wrap, are magnitudes better than the others (at least of the cartos I've picked up over the last month). They are hotter, produce more vapor, and the flavor is more intense. I'm glad I got the green coated ones first, or I would have placed the dual coils in the same category as all the other "also-rans" cartos I've used over the years.
I have some from 3 different vendors now, and unfortunately because I mixed them up, I can only tell where 20 of them came from. My original batch of green coated ones I got from Nhaler, the others I got from 2 other vendors, but because I mixed them up, I don't know which of the other 2 vendors also has the green coated ones now, so I don't want to say anything yet. I have 10 more coming in today from yet another vendor, so I'll be curious to see the internals and performance on those.
For the record, the the non-coated ones are not a total loss. They don't have a good punch on my ego batts, but run em at 5-6volts, and they perform as well as the others do on the ego batts. So I use those at home with my mods...