The batteries make a good impression. They feel good to the touch and the casing is not as sticky as with some other third-party batteries.
They are charged in their own charging cradle, which is operated via USB-C or Micro.
Both batteries can be operated at the same time.

In the test, one battery in my R10 lasts a good 1 hour and 15 minutes with a 4K25fps recording. My original Canon batteries do not reach these values, but they are also a bit older and only have 1040mAh. The Canon batteries last just over an hour.

It is important to remember that the K&F batteries, like all third-party batteries, do not have a status display of the battery charge in the camera. If you want this luxury, you will have to use Canon's own batteries. With the K&F (and other third-party batteries) the status display remains full until the camera simply switches off. Then the battery is also empty, of course.

I am happy with this battery set. Simply because the battery case is much more stable than my old third-party batteries. The charging cradle also seems well made.
As a cheap alternative (compared to Canon batteries) it is definitely worth considering. The only disadvantage is the missing battery status display mentioned above.