The Battery Boost will charge your handset, Bluetooth headset, mobile hotspot, mp3 player, and other micro USB devices. Providing up to 1 hour of additional talk time, the Battery Boost also doubles as a micro SD card reader. Carry photos, documents, and other digital media for access when you need it most. When the Battery Boost is placed within ANY USB port such as a computer, home or car charger, it will automatically charge its internal battery. You can even charge the internal back up battery and your handset at the same time! Built in clip allows for convenient carry options when not in use