Compact, lightweight, shockproof, non-slip and portable. Designed to fit the contour of iPhone 4G precisely. Can protect your iPhone 4G from scratches and dust. Easy access to all buttons, controls and ports without removing the case. Use it as a backup battery for your iPhone on the go or in an emergency. Built-in 1200mAh rechargeable Lithium-ion battery. Detachable case design for easy plugging. Compatible with iPhone 4G. Cell type: Lithium-ion battery. Capacity: 1200mAh. Standby time: up to 450 hours. Input Voltage: 5V. Output Current: 5V.