The Mili Powerskin is the worlds thinnest iPhone case with a built in battery. The Mili Powerskin almost doubles your iphones battery life, and isn't chunky or ugly like other iPhone cases. The Mili Power Skin gives you 19hours of audio playback, 5.4 hours of video playback and 230 hours of stand by. Not only does it greatly add to your battery life, the Mili Powerskin protects your iPhone from knocks and scratches with its hard shell case. The Mili Powerskin is certainly an essential purchase for your iPhone.