The Fitbit Alta HR is now available to pre-order and looks likely to be a best-seller in 2017.

The fashion-forward Fitbit Alta was an instant hit when it was released in March 2016, except it didn’t feature a built-in heart rate monitor. The new Alta HR changes that and redefines the form factor of wrist-based heart rate monitoring with the slimmest design to date.

On board the Alta HR is Fitbit’s PurePulse optical HRM which is one of the most accurate wrist-based BPM clockers. Along with 24-hour heart rate tracking, the new wearable offers all the essential quantified self metrics and improved sleep monitoring which tracks light, deep and REM sleep stages. The improved sleep features will also be available for other Fitbit wearables.

The Alta HR comes in a variety of color combos and has interchangeable bands to suit your mood. There’s also a range of accessory bands available and Designer labels; Tory Burch, Vera Wang and Public School also offer a line of Alta accessories.

The new super-slim fitness tracker keeps tabs on your steps taken, calories burned, distance walked, active minutes and shows your stats on a monochrome OLED tap display. The Fitbit app is loaded with features to help you achieve your fitness goals as well as torch unwanted calories and log food consumption.

It allows you to use heart rate zones while you’re training, and helps paint a picture of your overall cardio health by seeing how your workouts affect your resting heart rate.

The fitness tracker tells the time and date and offers customizable clock faces, automatic exercise recognition, and move reminders. It also displays incoming caller ID, text notifications, and calendar reminders.

The Fitbit Alta HR is 25-percent slimmer than its slightly older sibling, the Charge 2, and also lacks a few of its features, such as VO2 Max and GPS connectivity for those who run carrying a smartphone. Unlike the Fitbit Flex 2, the Alta HR isn’t waterproof enough to use in the swimming pool.

The Alta HR is sure to be a hot-selling wearable. It has a battery life of around 5 days between charges. The Fitbit app is compatible with iOS, Android, Windows and can also be accessed on your desktop/laptop.

It’s available to pre-order now for $149.95 – $179.95 from Fitbit.com and should start appearing in other retail outlets in a few weeks.