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. This charger battery pack provides you iPhone4 with an additional long hour for work. Feature 5000mAh capacity, the Mobile Power Source amounts to five to six mobile phone batteries, provides 30days standby time for your phone. Dual-USB design, the high capacity Mobile Power Source can be used to charge two devices at the same time! Great for travelling use! A great accessory you should have! Do not miss it!