Flexible, sustainable, powerful - that is what distinguishes our powerbanks from the Flex series. They feature six functions in a robust, water-resistant enclosure: They feature six functions in a robust, water-resistant enclosure: powerbank for charging mobile devices, charger for each inserted battery with charge level indicators, secure battery storage, two separate indicators for checking capacity, double safety function to protect against short-circuits and fast battery replacement. The Flex10 is powered by two 21700 batteries (supplied).