Very good battery and Cover

First, the battery itself: This course keeps much longer than the original. The charging speed is reasonable and fast (which usually is at the crux of cheap batteries from other manufacturers)

NFC I have not tested, so can not comment on it.

I (with a different cover) use two more batteries, I change the battery and the cover several times a week.
And so far, the cover is still in the state as the first day. So can not confirm a complaint in a recession that commented negatively about the cover.
One thing I have to say but to cover: Strangely enough, it comes from "below" (ie from the USB port) of a lot easier on / off than from "above". If one has in mind, one could rule out any damage already by some care itself.

Of course, the phone is heavier and thicker by this battery. Then is but curiously therefore better in your hand .... but it worse in your pocket. ;)

When using weight and thickness has no problem, this Battery + Cover is quite recommendable. If you have the size of the original S3 / 4 already problem, you should of course refrain from this product)