This is the newest release of Mili iPhone Spring 4 for iPhone 4. 2000 mAh, 25% more capacity than the 1600 mAh release! This is the world's thinnest iPhone 4 case with battery charger that MORE than doubles the life of your battery. Say goodbye to chunky additions to your iPhone that can make it uncomfortable or even nearly impossible for it to fit in the pocket of your pants. Carry it in your pocket with the Power Sping's sleek form fitting design anywhere you go! The Mili Power Spring 4 will extend the battery life of your iPhone by doubling its charging capacity. Enjoy your iPhone for voice, music, video, games and business applications with extended, stable power. You will now experience up to two days or more of uninterrupted iPhone power, depending on your usage.