Not only theirs, but basically everyone in the business. THERE ARE NO 'LEGITIMATE' 18650s for sale to end users like us. None. Even, technically, the ones from Arizer. There are only four makers in the real world that make premium 18650s (Samsung, Sony, Panasonic and LG), none market to individual end users. Only go guys making battery packs for cars, power tools and so on. Things with protective circuits built into them.
When your vape catches fire, they don't want to know you. Or your flashlight.
This also means 'everyone' has to buy from a secondary marketer, not straight from the maker. Counterfeits can slip into even the best sources. So stick with 'known good' sources?
I thought Arizer was high priced on their batteries so I went to the open market. This is what I found.
Batteries I bought from Arizer fit snugly almost airtight into my Air (I).
The aftermarket batteries had different diameters (in the same purchase order). I also noticed the girth of the after-market batteries seemed
correlate to their staying power.
The skinnier (after-market) batteries did not have the staying power of the batteries Arizer sent me.
I'm thinking Arizer accepts no culls when they purchase their batteries.
I recently bought an AirII and two extra batteries.
The extra batteries on the Air II were just like the batteries for the Air (I), in that their girth just barely allowed them into the battery chamber.
Based on the quality of the after-market batteries I got, I think it may be worthwhile to buy your batteries from Arizer.
I've also noticed that if you're buying Arizer batteries
the cheapest venue seems to be Arizer themselves even though some places sell the Air units cheaper than Arizer.
Also fresh batteries are essential for your Air.
Chuck your rechargeables when you notice they don't heat up as quickly as they did when the batteries were new. Extended/rapid blinking prior to a solid light is usually a good indicator that your battery is failing.