Inside of it. So basically it stays. In place like so you can remove it and this tiny portion here is the fitbit flex. Itself interestingly enough it's this tiny thing that houses all the components.

Fitbit devices track a variety of data related to your daily physical activity. This data varies depending on the device, but almost all of them track your daily steps, distance, calories burned, and sleeping activity.

Product information

May 2013 In May 2013, Fitbit released the Fitbit Flex, the first Fitbit tracker worn on the wrist. It tracks movement 24 hours a day, including sleep patterns.

The Bottom Line. Among wrist-worn activity trackers, the Fitbit Flex is the best and most competitively priced one you'll find. If you're not stuck on wearing a bracelet, though, the Flex's close cousin, the Fitbit One, is the obvious choice.

It should work, but there are times a Fitbit won't spring back to life after having a dead battery for a long time. Might be a good idea for you to charge it up and see how it goes. Some people on the forums still use a Flex, but it was retired quite a few years ago.

• Google Apps.
• Daily Readiness Score.
• Health Metrics & SpO2.
• AFib Assessments.
• Stress Management.
• 24/7 Heart Rate.
• Sleep Tracking.
• Active Zone Minutes.

Fitbit's line of wearables does just about everything. From tracking daily steps and workout paces to monitoring sleep patterns and stress levels, the best Fitbit is designed to help you better understand yourself. And there are a number of different Fitbit models designed for different users.

Some people on the forums still use a Flex, but it was retired quite a few years ago.

The battery in Fitbit Flex 2 can last up to five days*. Learn specific ways to extend its battery life and then develop a charging strategy so that a drained battery doesn't leave you trackerless. In your Fitbit.com settings, you can sign up to receive a push notification on your mobile device or an email (or both!)

In 2013, Fitbit introduced the Fitbit Flex. This device could track movement 24 hours a day, measuring steps, distance, calories burned, and active minutes. It was a minimalist and water-resistant device that used LED lights to display progress towards daily goals.

Fitbit trackers aren't meant for the most hardcore of athletes, but they're still excellent devices for tracking overall activity as well as monitoring certain health and wellness metrics like EKGs and blood oxygen levels.

Easy to use, comfortable to wear, and jam-packed with health-tracking features, the Fitbit Charge 5 is our favorite fitness tracker. It's small enough to satisfy those who prefer the size of a fitness tracker over a smartwatch. Still, it has a screen large enough to comfortably swipe through your stats on the device.

While the Flex 2 was one of the least accurate devices in our review - we still believe this pedometer proves a worthy recipient of the 2018 Editor's Choice Award.

It is the heart of your device and there is no replacement for it. The Flex 2 was discontinued, so places who do sell them are really raising the prices for them. Have you seen the new Inspire series? It is similar to the Flex, but it has numbers rather than dots.

Fitbit trackers are equipped with photoplethysmography sensors, which is the small green light you see blinking on the tracker's underside. This light essentially monitors the volume of blood in your wrist and uses that to calculate the number of heartbeats in a minute.