Used for wireless syncing via a PC.
Compatible with Fitbit One, Zip, Flex, Flex 2, Charge HR, Surge, and other older Fitbit models.
Purpose: Syncs activity data from the tracker to the Fitbit app on a computer.
Used to charge a tracker — likely for Fitbit Flex or Flex 2.
Not interchangeable with other Fitbit models — the charging cradle is model-specific.