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(Pocket-lint) - The Flex 2 is the sequel to the Fitbit's original all-day activity-tracker. It brings together fitness-tracking and sleep-tracking into a simple yet stylish wrist-worn design.

It isn't as feature-rich as the company's Charge 2 or Blaze, it doesn't have a display like the Alta, but the Flex 2 does have its own attributes that make it a great little activity tracker. Here's why.

Fitbit Flex 2 review: Design

  • Removable tracker (31.7 x 8.9 x 6.8mm)
  • Fits into one-size, lightweight elastomer band
  • Colour options: black, lavender, magenta, navy

The Fitbit Flex 2 is a small, slim and subtle-looking activity tracker, making it a great choice for those who want to track activity with an unobtrusive device. It's considerably slimmer than the Alta, Charge 2 and the original Flex, sitting comfortably and discreetly on the wrist.

Like its predecessor, the Flex 2 is made up of a small removable tracker housed within an elastomer band as standard. It is removed by simply slipping it out from the underside of the band and it can even be placed into specially-designed accessories (sold separately) for a smarter look.

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The standard elastomer band is textured rather than smooth. It features a chamfered edge, tying it in with Fitbit's aforementioned devices. There are four colours available - black, lavender, magenta, navy - all of which use a form of two-pin fastening rather than a buckle like the Charge 2.

The fastening mechanism of the Flex 2 is significantly more secure than the original device and other two-pin devices we have tried. Once on, it's difficult to get the Flex 2 off without really tugging. It's not going to go flying off anywhere.

Unlike the Alta and Charge 2, the Flex 2 foregoes an OLED display for five LED lights that shine through the elastomer band to display your progress, with each LED representing 20 per cent of your set goal. These lights, which sit vertically rather than horizontally as they did with the original Flex, are also used for smartphone notifications and reminders to move.

Fitbit Flex 2 review: Features

  • Waterproof with automatic swim-tracking
  • SmartTrack for auto activity recognition
  • Smartphone notifications via LED lights

The Flex 2's greatest attribute is that it's Fitbit's first and only waterproof tracker, allowing for swim-tracking. It measures duration and laps for freestyle, butterfly, breaststroke and backstroke.

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It will also measure steps taken, distance travelled, calories burned, active minutes and sleep duration when out of the pool, just as we have come to expect from most activity trackers.

Fitbit SmartTrack means the Flex 2 can automatically recognise certain activities - such as walking, running or swimming - but it doesn't offer elevation data, heart-rate tracking or any form of GPS (global positioning) tracking.

As we briefly mentioned, the Flex 2 does have smartphone notifications in the form of call and text alerts, as well as reminders to move and silent alarms. All are presented via colour-coded LED lights.

It will vibrate and the LED lights will flash, with one turning blue for calls, purple for text messages, pink for reminders to move and orange for silent alarms. It takes time to get used to the different colours and what they mean.

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Of course, the notifications aren't as useful as they are on the Charge 2 or Alta, and there is still no third-party app support, but the Flex 2 does categorise WhatsApp calls as normal calls - so you will get handy alerts for those and know to go digging for your phone.

As there is no display, however, the Flex 2 won't show who is calling and, of course, there's no actual text to read. If you want that then look towards the Fitbit Alta or Charge 2.

Fitbit Flex 2 review: Performance

  • No GPS limits accuracy
  • Five-day battery life

The Fitbit Flex 2 is a good performer when it comes to basic activity-tracking. Its accuracy is on par with the Fitbit Charge 2 when it comes to step-tracking, the SmartTrack feature works well by recognising the correct activities without a problem. For example, the Flex 2 knew when and for how long we were doing a resistance workout in our living room, compared to walking to the station.

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Calories burned is harder to determine in terms of accuracy, while distance travelled is never spot-on unless GPS is playing a part, which means the Flex 2 won't be great for runners.

Sleep data coincided with when we went to bed and when we got up, though sometimes the Flex 2 couldn't distinguish between waking up and getting up, suggesting we were still asleep when we were actually reading emails or stalking on Facebook.

In terms of battery life, Fitbit claims the Flex 2 will offer up to five days, which isn't far off what we've been getting. With all notifications and regular exercise, we got between four and five days of use.

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Be sure to put the tracker into its charging module the right way though - as we placed it incorrectly a couple of times which resulted in no recharging. Cue dead Flex 2 when leaving the house.

Fitbit Flex 2 review: App

  • Setup personal goals
  • Challenges to keep you motivated
  • Edit dashboard to suit your goals

The Fitbit app is one of our favourites in the activity-tracking field thanks to its simple interface and easy-to-navigate platform.

No matter what Fitbit tracker you have, the app layout is the same but features will vary, depending on what your device is capable of tracking. For all devices, there are four tabs at the bottom of the app: Dashboard, Challenges, Friends and Account (along with a "+" for quick access to tracking an exercise or logging weight and food).

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The Dashboard tab presents a summary of your day, with everything from steps taken and calories burned to sleep duration and active minutes. There are tiles for data such as water intake, food intake and weekly exercise, each of which can be edited into a display order that suits you by tapping "Edit" at the bottom of the tiles.

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As is the case with the Charge 2, some features could be easier to find, such as activities recognised by SmartTrack (which are hidden within the weekly exercise tile) but the majority of settings and features are visible upon first glance.

A small image of the Flex 2 is present in the top left-hand corner of the app, along with a battery indicator. Tapping on this will launch settings - including the hand you are wearing the tracker on, main goal preferences and smartphone notification options. You can also tailor reminders to move here.

The Challenges tab offers various challenges to keep you motivated, as well as an Adventures feature that launched with the Flex 2 and Charge 2 (which is also available on the other Fitbit devices). This feature enables you to explore destinations by working towards a different step goal every day, based on your seven day average.

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Last but not least is the Account tab. Here you can edit your profile, change your goals, link third-party apps such as MyFitnessPal, and alter things such as stride length for better accuracy.


The Fitbit Flex 2 is a simple yet effective tracker with a more exciting design than its predecessor. Not a great deal has changed in terms of looks, but Fitbit has done enough to ensure the new-generation model doesn't look like a boring rubber band. The far better two-pin clasp ensures a solid, comfortable fit too.

The addition of basic smartphone notifications and waterproofing is also welcome, and we love that Fitbit has continued to embrace the fashion angle with more interchangeable accessories to smarten up the Flex 2's potential too.

The Fitbit Flex 2 has a good thing going on: it's simple, stylish and unobtrusive. It won't be for those who want more data such as heart-rate or GPS tracking, but it's a great device for those after basic tracking.

Fitbit Flex 2: Alternatives to consider

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Fitbit Alta


The Fitbit Alta is similar in size to the Flex 2, but with a slightly higher price tag and an OLED display, meaning data and smartphone notifications can be read. Interchangeable straps allow the Alta to be a little smarter and basic activity tracking is great. It doesn't offer as many features as the Charge 2, though, and you also miss out on the waterproofing of the Flex 2.

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Fitbit Charge 2


The Fitbit Charge 2 is larger, bulkier and more expensive than the Flex 2 - but it offers a few more features, such as heart-rate monitoring, VO2 Max data and Guided Breathing. Its smartphone notifications are also more useful thanks to the built-in display and the interchangeable straps enable you to make the Charge 2 look smarter.

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Garmin Vivosmart HR+


The Garmin Vivosmart HR+ is quite a lot more expensive than the Fitbit Flex 2, but like the Charge 2 it too offers several more features with both heart-rate monitoring and GPS tracking on board. It's a great device for those who wants to track daily activity as well as record runs or walks in a little more detail but who don't want to wear a big running watch. 

Writing by Britta O'Boyle.