DHMXDC Replacement Bluetooth USB Wireless Sync Dongle Compatible Fitbit Flex/Flex2/Alta/Force/One/Charge HR/Surge/Charge 2/Blaze Activity Trackers Compatible with Fitbit One/Flex/Charge/FORCE/Charge HR/Surge/Blaze/Alta and Fitbit Charge 2 Flex2 activity tracker. USB Dongle Bluetooth to replace the Fitbit cable. Synchronize Fitbit data wirelessly. With output short circuit, over voltage and overload filter protection prevent your device being damaged by overcurrent. NOTE: It does NOT work for FITBIT ZIP MODEL, please pay attention to it before you are buying. Note: The best syncing distance between the fitbit tracker and dongle is within 1m(3.3 feet) .