Sabrent Slim Credit Card Sized Charge Card Adapter for Micro USB with 400mAh Emergency External Battery Backup Charger Power Bank Charger (PB-RSCC) Only 3mm thick, easily fits into your wallet. Android and Micro USB charging cable, the size of a credit card. Works with all Android and Micro USB powered devices. Provides cell phones up to 4 hours of extra power and up to 3 hours for smartphones. Extremely lightweight and compact.