It´s agood case for the Iphone and aou can charge it seperatly through pushing the Button on the back. In my Opinion you can Charge your Phone one or two times with this. 6000 mAh is not realistic.
I got this cheaper through a Coupon.(10 €)
You have to watch out, that you don´t break it when you remove it from the lightning Port. It bends and can break.