Samsung S4 Phone and Battery Power Bank Case with Built-in Extra Battery and Flip Cover (White) Compatible with Samsung Galaxy S4. Replaces your phone back cover, does not increase bulkness of your phone. Slim fitting and weightless, with maximum battery life extension Built-in extra rechargeable battery (2400 mAh), back to back connected to your internal battery, extends the battery life of your smart phone Built-in flip cover case to protect your phone screen, with home button and access to volume control for easy operation LED light indicator for low battery and charging status