Personally, for my 4s I picked up the Lenmar battery case. I found the shape to be better that the mophie and the battery was 1800mah I believe. Also, they were only like 35$ from groupon/amazon/ebay shop so it was about 1/3 the price of the mophie. It worked quite well for the 1.5 years I had the 4s, and when I moved to the 5s, I simply ordered the same one again - but for the 5s. Was 32$ on groupon. For the money, i'd get one like that over the mophie or at least find the mophie on HEAVY discount at this point. 4s is EOL, so they should be fire selling the cases like crazy