Keystone Holster H1.4 ECO Holster Rechargeable Battery Case for iPhone 4 and iPhone 3G/3GS - Holster - Retail Packaging - Black Built-in 1400 mAh, rechargeable Lithium-polymer battery. Automatically recharges iPhone 4, iPhone 3GS and iPhone 3G once it is in the holster. Doubles the battery life of your iPhone. Hard case protecting your iPhone while it is not in use. Apple "Made for iPhone" certified.