Our battery packs have been thoroughly tested in the most extreme elements to ensure quality and reliability. Many battery packs claim to be a certain size and capacity, but after testing you will find that they fall far short of their specifications. We guarantee that you will be getting the highest quality battery pack that is the capacity specified. Whether it is a 10,000 mAh or 20,000 mAh, what you see is truly what you get. With the 20,000 mAh you will actually last up to 16 hours with settings on high. AND it will charge your phone at the same time.