Calibre - ULTRA'GO mini is a portable charger battery (power bank) for iPhone, iPad, iPod and other USB-powered devices. This gadget fits easily into any pocket with its ultra-slim, lightweight and easy-to-hold design offering ultimate portability, whilst the screwless aluminum alloy enclosure provides outstanding protection. The “Vibration Signaling” feature indicates battery power status by varying vibration patterns. Vibration Signaling: four vibration alerts – 100% battery charge level, three vibration alerts – 75% battery charge level, two vibration alerts – 50% battery charge level, one vibration alert – 25% battery charge level.