V4L's carts are confusing!
Their blanks:
Coolcarts are 3.2(?) ohm, cooler on the lips, I think the vapor is still plenty warm for me (these I like)
WOW carts are 2.8(?) ohms, hot on my lips, hotter vapor and some say more TH
A variety of blank (empty) cartomizers for Vapor King and other KR808D-1 style E-Cigs
But their prefilled carts... as I barely understand it
WOW carts are just one or the other kind of cart filled with one of their WOW juices - like I am pretty sure the WOWBoy I got in a cart sampler was in a WOW cart, and the WOW 555 was in a Coolcart
The rest of their carts - I have no clue which carts they use. Maybe different kinds for different juices?
I think some prefills say they are Coolcarts.
In any case, if you get one that is too hot on the lips for you, just cut a hole in the end of a carto condom (the stretchy covers that are shipped on each end of the carto) and then out it back on the carto mouth end as a lip guard.
They don't make it very clear.
Cartos do not last as long as the liar sites say they do. The ripoff rebranders like to say a carto lasts as long as a pack of cigarettes or even 1 1/2 packs and both amounts are laughable and just not true. I think even if you ran a carto dry you would not get that much out of it. I think you can get 5-6 (or a bit more if it was filled well) cigarette's worth of drags out of a standard stuffed carto before noticing reduced vapor or a hit of bad taste and then it's time to add more juice. That is how you will get the most life out of a carto. I have been vaping one carto all day (and I was a 1.5 PAD smoker so I have vaped it about a pack's worth so far) and I think 4-5 times today I popped out the mouthpiece cap and carefully dripped some more juice down the inner sides of the carto, rotating it to drip on all side while avoiding the middle air hole. I am making sure I keep it damp to get best life out of it. However, I do no have the patience to drip and wait drip and wait to see how much i can fit in there so I am mainly just keeping it damp.
I have never vaped one dry to the point of singeing the stuffing so I don't know what the absolute max you might get out of one is if your intention was to use it once and throw it out when you singed the stuffing or killed the atty.
BTW I am using manual batteries so I think I get pretty good efficiency - no weak, warm-up or non-productive drags.