Whether you are a backpacker or a cellphone fan. If there is a compact and practical and portable mobile phone battery in your pocket, that will be great! You can take portable battery anytime and anywhere. The charger battery source is inconspicuously onto the back of iPhone4 4S. This charger battery pack provides you iPhone4 4S with an additional long hour for work. Featuring 4000mAh capacity, the Mobile Power Source provides 30days standby time for your phone. USB port design, great for travelling use! A great accessory you should have! Do not miss it!
Pros:small size, easy charging via USB port-no extra adaptor needed
Other Thoughts:I used it for the first time during my weekend under the tent. I charged my Xperia ArcS battery (1800 mAH) twice and battery pack has still some energy. So I suggest the mentioned capacity is real.