Wow! I'm impressed with this small, yet powerful combination of batteries and charger from Smatree. In my Gopro 3+ Black it outperformed the OEM battery each and every time. I've gotten between 2 hours and 2 hours 12 minutes from a full fresh charge on the Smatree batteries, while the Gopro each time has always been a few minutes short of that.
In fact, I have the impression that the charger is faster than the Gopro in-camera charging system and may even be a bit more complete, and that's using it through the same computer power source USB cabling. So it's directly comparable.
Summary: a very inexpensive replacement for Gopro batteries at a very cheap cost!