Please don't use these batteries!
Yes they are 18650 but thats just the size, everything else is different and not just a little, they are
LiFePo4 (a lot more risky than IMR) and 3.2v so charging with Air or 'normal' charger runs the risk of these going boom. Remember the air charges to 4.2v (full)
Now the S2 is more like the OEM air battery although i cant see enough info on that site to say how much like them they are, i would always advise OEM batteries for the air, others will work but you will never gain anything other than a cheaper price with them, performance will be the same or worse, there might be some that do give more but it will be such a small difference you would probably never notice unless timing down to the second and even then there are other things (like heat up time) that can/will be affected.
The choice you have to make is either pay a little more for OEM's and know 100% your warranty is ok, or save a little money and always be wondering can arizer tell if I've used other batteries? (Now they probably cant but are you sure?)
Remember these batteries will last a good while so over the life the cost is nothing really IMO, and like others here i see it as I've paid all this money for my air and why cheap out on the most unstable part, maybe unstable is the wrong word but the battery is the only thing that could cause harm if used incorrectly or if bad quality.
I also want to point out I'm not saying all other batteries out there are dangerous or low quality, i have and use many others in other things, but users should get a minimal understanding of any risks from using these kind of batteries (what can go wrong and why/how it can)
Years ago when i first used 18650's in torches i bought cheap torches from china and went with the cheapest batteries i could get, now i consider myself lucky that nothing went wrong knowing what i do now.
I have bought, used and tested a whole load of 18650's 18350's 14500's 26650's and have found that the cheaper the battery the more chance its not what it claims to be.
Always stay away from batteries with fire in the name (this should ring warning bells anyways come on
fire + battery = no good)
I have tested some claiming to be protected but they have no PCB, some that claim 5000mAh that meter out at under 1000mAh and thats just the basics not even getting into C rating or chemistry.
In summary whatever batteries you get make sure you get them from somewhere you trust and treat them with respect.
Just my
Wow thanks for an amazing, concise answer, I love this community. I haven't got my air yet but I had these batteries laying around just thought I'd check to see if they work, and I'm glad I did