The new WSD-F21HR from the Casio the PRO TREK Smart series is an outstanding smartwatch for efficient, effective fitness training, as well as mountain climbing and trekking. The heart rate monitor is great for pace management during activities such as road running, trail running and cycling.

CASIO entered the smartwatch market in 2016 and released the WSD-F20 in 2017. Featuring GPS technology and offline maps, this and subsequent models allowed users to easily check their current location from their wrist, even in locations without cell phone service, and they have been especially popular.

The new CASIO PRO TREK WSD-F21HR offers a new heart rate monitor together with the wearable map technology, enabling wearers to continually check their physical condition, or navigate unfamiliar routes.

Running and Trail Running menus have been added to the Activity app, which displays measurement data in real time. The user can optimize the data displayed by choosing three types of information such as heart rate, pace, and distance to display on the watch.

Furthermore, because up to four screens can be set, the user can easily switch between them and check the desired information during the activity.

In addition, it comes with a new Heart Rate watch face. Using an accelerometer, the WSD-F21HR automatically switches to the heart rate monitor screen when motion is detected. The heart rate information is expressed as five heart rate zones, allowing the user to see this data at a glance.

By setting the maximum and resting heart rates, current fitness and training results can be shown as five levels. The target exercise intensity can be checked with the heart rate zone screen, allowing the user to determine the ideal heart rate for the target training, or the user’s current fitness level.

As with other PRO TREK Smart models, the new WSD-F21HR can use Google App services, the trekking app ViewRanger, the cycling app BIKEMAP, the running app STRAVA, and other outdoor sports apps compatible with Wear OS by Google.

Main Features of the WSD-F21HR

First heart rate monitor in a PRO TREK Smart model

The new model is equipped with an optical sensor that measures heart rate by flashing LED light into the wrist. A new Heart Rate watch face automatically switches to the heart rate monitor screen when motion is detected by the accelerometer. The measured heart rate information is expressed as one of five heart rate zones, allowing the user to see at a glance the elapsed time and heart rate information.

New activities: Running and Trail Running menus

The displayed data (upper, middle, and lower sections of the screen) for road and trail running in the Activity app can be customized by the user. Information choices include heart rate, pace, and distance, and up to four screens can be set. The user can easily switch between the preset screens and check the desired information while engaged in the activity. Since a map and current location can also be shown, users can enjoy taking an unfamiliar route, or running when they are traveling away from home.

Route import and data upload for greater device enjoyment

Since the WSD-F21HR can import GPS log data, the user can check running, trekking and cycling routes they or friends have used in the past. In addition, data measured by the Activity app is automatically saved to Google Drive, and activity history can be viewed on Google Calendar.

Durable for broad outdoor applications

As with other PRO TREK Smart models, the new WSD-F21HR is designed for outdoor use. It is water resistant to 50 meters and built tough enough to meet United States Military Standards.

Design with a focus on outdoor sports

Featuring a front bezel that looks bold and sporty, the exterior design combines flexibility and durability. A soft urethane band and a double pin buckle ensure a very comfortable fit. The WSD-F21HR offers practical performance designed to delight everyone who loves outdoor sports.

Technical details

WSD-F21HR-BK: Black

Size of Case: Approx. 61.7mm×57.7mm×16.8mm (H×W×D)
Water Resistance: 50 meters
Environmental Durability: MIL-STD-810 (United States Military Standards issued by the U.S. Department of Defense)

1.32-inch dual layer display
Color TFT LCD and monochrome LCD
Color: 320×300 pixels
Touchscreen: Capacitive touchscreen (anti-fouling coating)

Compatible (including GLONASS and MICHIBIKI (QZSS))

Color Maps
Compatible (supports offline use)

Pressure (air pressure, altitude) sensor, accelerometer, gyrometer, compass (magnetic) sensor, optical sensor (PPG Heart Rate)

Other features

Wireless Connectivity
Bluetooth® V4.2 (Low Energy)
Wi-Fi (IEEE 802.11 b/g/n)

MAP button, Power button, APP button

Lithium-ion battery

Charging Method
Magnetic charging terminal

Recharging Time
Approx. 2.5 hours at room temperature

Battery Life (When GPS Not in Use)
Normal use (color display): 1.5 days, roughly
Multi Timepiece Mode (timekeeping and sensors only): 1 month, roughly (Varies according to use)

Approx. 81g (including wristband)

Operating System
Wear OS by Google
Operating Environment: Wear OS by Google works with phones running Android 4.4+ (excluding Go edition) or iOS 10 or later. Supported features may vary between platforms and countries.