Keep your cell phone, MP3 player -- and other devices that charge via USB -- powered up at all times with the Juice Box Ruby Backup Battery Charger. It s easy to use - simply charge the backup battery charger using the included Micro-USB cable, and then connect your device via the USB 2.0 port for an extra boost. Slip it in your purse or bag and be on your way. The backup battery charger is available in several vibrant, fun colors and will keep your device working at optimum performance levels at all times.