These Sofirn 21700 cells from Aiexpress are just slightly different then the single Sofirn cell I received with my Sofirn C8F. The original cell has a perfectly smooth bottom and the new cells have a circular ring indentation in their bottom. I didn’t spend a lot of time comparing them but that was all that really stood out.
The new cells all read 14mOhm or 15mOhm on my XTAR Dragon. Testing in my Texas_Ace lumen tube, fresh off the charger, the original cell gives me around 2300 lumens and the new cells around 2500 lumens. My Shockli 21700, 4000mAh cells are 18mOhm and run around 2400 lumens in the C8F.
I paid $12/cell for the Shockli cells and I paid $4/cell for these Sofirn batteries. I think I got a pretty good deal so far.
I’m running a capacity test on my Opus charger now. It won’t be dome until tomorrow.

I just checked and the sale pricing is still in effect.