The BLK22 batteries are of the usual K&F Concept quality. They don't look cheap, the outer shell actually looks more robust than the original.
They charge well via the USB-C port (or in the charger or camera) and have a decent battery life that even slightly exceeds the original battery.
The USB-C port is particularly practical if you want to travel more easily and want to charge the battery with a power bank while on the go. Interestingly enough, the additional connection doesn't seem to hurt the battery capacity.
Due to the bright color, they are also a bit harder to lose;)
The batteries come as a “set”, i.e. 2x the same box. This means that a total of 2 USB-C cables are also included for charging. I would actually have found it a bit better if a two-part cable was included to charge both at the same time.
I use them both in my S5II and in my older G9 (BLF19 batteries) without any problems.
But - as with all BLK22 batteries - these cannot be charged with BLF19 chargers. I would be interested to know whether the USB-C port also does the balancing, which is often missing from cheap chargers, but could not find any information about this.