The Fitbit Flex consists of the following parts: LEDs in a light guide that are used for display purposes, a Bluetooth antenna, a small battery, a vibrator that functions as the device's alarm, a near field communications antenna and a motherboard. All of these parts are contained within the Fitbit's plastic casing. The Flex also comes packaged with several other items, including two adjustable wristbands, a wireless sync dongle and a USB charging cable.
The Fitbit Flex's Bluetooth antenna is intended for communication with both the Fitbit's dongle and other wireless devices. The battery recharges via waterproof interconnects on the motherboard and lasts for up to five days per charge. The near field communications antenna allows the Fitbit to connect with other NFC enabled Android devices. Soldered directly to the Flex's motherboard are a microcontroller and three interconnects of various functions.
Other Fitbit wrist wearable devices, such as the Charge, Charge HR and Surge have different parts breakdowns. The Surge, for instance, includes several screws and metal pieces, a GPS antenna, a touchscreen controller, and an LCD, in addition to many components similar to those found in the Flex. Customers also receive a wireless sync dongle and a USB charging cable when purchasing a Surge.