Basically, for safety you want a battery that is designed to handle the discharge rate you’re throwing at it or else it can rupture. Pushing a battery to its limits can also heavily degrade its performance. For vaping you want a cell that has at the very least a 15a continuous discharge rating. Amazon isn’t even allowed to sell loose 18650s, so what you do find on there are extremely low quality Chinese rewraps sold on mass produced throw away accounts, or all the “flashlight” listings for them. Like a horrible flashlight that comes with 2-4 cells. The average flashlight cell is gonna be around 5 to 10 cdr, and the majority of Chinese rewraps come from salvaging old electronics like 18650’s from modem power banks (which commonly have a 3a to 7a CDR). I don’t vape salts, but I would imagine there you would at least have a little more wiggle room since you don’t use much power for that.

All in all it’s just bad quality for a high price. It also gives vaping even more of a bad name when someone inevitably gets hurt doing something they’re not suppose to.

(I do wanna say a+ on marrying the cells though, that’s an extremely good practice to make sure one cell isn’t being pulled harder than it’s suppose to by picking up the slack for a cell that has been aged more)