Portable, compact and simplicity. Plug-in design and very convenient to use. Non-slip and comfortable grip design. Equipped with 4 LED charge status indicator lights. Custom fit for the contour of iPhone 4G precisely. Designed for use on the go or in an emergency. Used for charging your iPhone 4G anytime and anywhere. Extend the working time of your cell phone. Built-in 2000mAh lithium battery. Can use a USB cable to charge this battery. One switch on/off button for easy operation. Compatible with iPhone 4G. Capacity: 2000mAh. Input voltage: DC 5V. Output voltage: DC 5V.