One of Casio’s classic outdoor tool watches returns with its signature triple-sensor design, in an all-new environmentally friendly biomass plastic case.

Designed to assist with navigation wherever your treks may take you — no mobile phone required. The new Pro Trek PRG-340 collection features the usual timekeeping functions found on most multi-function Casio wristwatches, such as hour, minute, second, AM/PM, month, date, and day — plus an advanced digital altimeter, barometer, thermometer, compass — and additional features (listed below), all housed in a sustainable biomass plastic case, and a solar-powered Japanese quartz movement accurate to -/+ 15 seconds per month.

2022 Casio Pro Trek PRG-340

There are three models available: the PRG340-1 (black with orange accents), PRG340-3 (dark green with yellow accents), and PRG340T-7 (gray titanium with black accents). For this test, conducted both in the field, at multiple outdoor locations, as well as in the studio, Casio loaned us the black and orange PRG340-1 model.

Looking West from Lookout Mountain Colorado

Field Report

For this field report, I chose a short hike at Lookout Mountain Park, which is relatively easy compared to Loveland Pass. Lookout Mountain, in spite of its name, is technically a foothill. Situated on the eastern flank of the Front Range of the Rocky Mountains, Lookout Mountain is located 1.7-miles West-Southwest of Golden, Colorado, and approximately 30-minutes by car from Downtown Denver. It’s a nice quick escape from the city. With a 2,000-foot change in altitude from Denver which is 5,280 feet at Capital Hill, the air is far cleaner than in the city, however, on this particular bright sunny November day, the temperature was in the low 70s, just like Denver. The mountain air was incredibly fresh and invigorating and the temperature was perfect.

2022 Casio Pro Trek PRG-340-1

Eco-Friendly Case

The Pro Trek PRG-340 is offered in a 51.7 mm x 15.1 mm biomass plastic case, with a biomass caseback and biomass strap (except for the PRG340T-7 which has a biomass case, caseback, and a titanium bracelet). The Pro Trek PRG-340 watch has a lug-to-lug length of 54.7 mm and a lug width of 23 mm. The biomass plastic straps are non-tapered, while the titanium bracelet tapers down from the lugs to the clasp.

2022 Casio Pro Trek PRG-340 wristshot at Lookout Mountain facing West

Biomass plastic is made with organic resources such as plant-derived castor oil plants and corn, which reduces the ecological footprint and is Earth-friendly. According to Casio, “Biomass plastics are polymers produced using the chemical or biological synthesis of materials sourced from plant matter or other renewable organic substances and are widely thought to help reduce environmental impact and promote the shift to a circular economy.”

Lookout Mountain View of Denver Skyline

While there are no crowns, large dedicated buttons, that can be operated even with gloves, provide an ergonomic way to interact with this tool watch. Offering further utility is a movable lug design that enables the watch case and band to be laid flat, and that’s useful when working with paper maps, checking where you are and where you’re going. This movable lug structure also makes the watch sit more ergonomically on the wrist. And while the thinner design of the case enhances the comfort as well, do note that the 54.7 mm lug-to-lug measurement results in a profile that will go over the edges of the top of your wrist, although for a tool watch, this is not unusual.

2022 Casio Pro Trek PRG-340 caseback

Four screws secure the caseback. Another four screws are placed at the corners of the watch on the front side, although it’s not clear if they’re functional screws. Visible screws on the caseback are relatively common, however, on the front, they seemingly take away from the aesthetics, although the designers may have been going for an industrial look.

2022 Casio Pro Trek PRG-340 flat lay

A mineral crystal, which is set below the plane of the bezel (armored), protects the dial. There are openings on the left side of the case, which are required to take the barometric pressure and temperature readings, however, no water gets in thanks to a water-resistant membrane. The watch is water-resistant to a depth of 100 meters.

Casio Pro Trek PRG340 1 side angled


Like with the Mudmaster GWG2000-1A that we tested in-depth last year at Loveland Pass and in Denver, the ability to measure direction, air pressure, temperature, and altitude are all available via direct buttons. This is done with three sensors: a pressure sensor, a magnetic sensor, and a thermo sensor built into the watch. The compass uses a magnetic sensor. Altimeter readings are based on the pressure sensor (conversion of air pressure reading to altitude reading based on ISA values). And when the user enters the Barometer/Thermometer mode, the watch utilizes both the pressure sensor and thermo sensor. Compared to the aforementioned Mudmaster, the screen on the Pro Trek PRG-340 is all-digital (versus analog-digital), not to mention the screen is much larger, and the buttons are knurled for slip resistance, and located all on one side of the case, making them easier to access.

Lookout Mountain Facing West

Solar Powered

Unlike some earlier Pro Trek models, this version has the convenience of solar power. Sunlight enters through solar cells on the translucent perimeter dial, automatically recharging the battery-powered quartz movement. Once fully charged, the watch can operate autonomously, without any light, for up to 7 months while being used, or up to 27 months if not being used while in power save mode.

2022 Casio Pro Trek PRG-340-1 compass wristshot

Digital Compass

Casio upgraded its latest Pro Trek with a dual-layer LCD that uses separate layers to display the compass graphic, simultaneously with the time and various measurements, allowing for a larger compass display, better legibility, and easier navigation in a design that’s both functional and aesthetically pleasing. In conjunction, with the digital compass, which bases its reading on a magnetic sensor built-in to the watch, uses three reverse pointer-shaped hands to mark true North and single pointers to mark East, South, and West, there’s a bi-directional rotating bezel with compass markings that can be quickly aligned with the digital compass points to continuously mark your direction as you move.

2022 Casio Pro Trek PRG-340-1

The rotating bezel moves very easily, without a firm click as you find on a typical dive watch. Though even without the safety of a clicked bezel, once positioned, the bezel always stayed in place for me, which was reassuring in spite of the minimal effort required to move it. I did not get a chance to test rotating the bezel with gloves on, but it’s presumably designed to be operated without or without gloves, just like the three sensor buttons are oversized so as to be easily operated with or without gloves on.

2022 Casio Pro Trek PRG-340 wristshot by South Platte River

Digital Altimeter

Altimeter readings are based on the watch’s built-in pressure sensor (which converts an air pressure reading to an altitude reading based on ISA values). You can use the digital altimeter to take an altitude reading at your current location. You can also record the altitude, along with the date and time measurement. And you can measure the altitude differential between two points. Further, the bar chart above the altimeter readout shows your change in altitude.

2022 Casio Pro Trek PRG-340 barometer thermometer


When using the Barometer/Thermometer mode, the watch utilizes both the pressure sensor and thermo sensor. You can display the current barometric pressure at the press of a button, which can alert you to noteworthy pressure changes. Using the “BARO” button simultaneously gives you an air temperature reading just below the larger barometric reading on the dial. The temperature can be measured down to as low as 14 degrees Fahrenheit, at which point anything colder will register an “error” message. However, even if the temperature function stops working, most of the other watch functions should continue to work.

2022 Casio Pro Trek PRG-340 Super LED illuminated

Additional Functions

The Pro Trek PRG-340 series offers World time with 31 time zones (48 cities + coordinated universal time), daylight saving on/off, Stopwatch with 1/10th of a second accuracy, with a measuring time of up to 1,000 hours, and it can run in three models (elapsed time, split time, 1st-2nd place times), Alarm 5 daily alarms (with 1 snooze alarm), Hourly time signal which can be turned on/off, Mute feature allows you to turn button operation tone on/off, Battery level indicator lets you monitor how much battery power is remaining, Timer Countdown timer that’s accurate to 1-second, with a countdown range of 24 hours, and start time setting range between 1 minute to 24 hours (1-minute increments and 1-hour increments), Light LED backlight (Super Illuminator) Full auto LED light, selectable illumination duration (1.5 seconds or 3 seconds), afterglow, Calendar Full auto-calendar (to the year 2099), Energy Saving mode Power Saving (display goes blank to save power when the watch is left in the dark), 12/24 Hour Format allows you to display either regular or military time, Sunrise/Sunset indicator lets you know precisely when sunrise and sunset will occur each day.

For full details about every function of the Pro Trek PRG-340, there’s a 34-page Operation Guide.

2022 Casio Pro Trek PRG-340 Light button close-up


Getting out in nature always seems to be a positive experience and the moment I felt the incredibly clean mountain air at 7,200+ feet, I remembered, viscerally, why we need to reduce the use of anything bad for the environment.

Powering the Pro Trek with sunlight is one way of reducing the ecological footprint. The other is by manufacturing products with sustainable plant-derived products such as this biomass case.

Not only is the product green, and more feature-rich than its predecessors, but Casio has also delivered a slimmer more ergonomic watch, with an all-new dual-layer display that greatly enhances legibility.

The triple-sensor design makes the Pro Trek an excellent purpose-built tool, however, while the dedicated three-button layout is great for directly accessing the altimeter, compass, and barometer — accessing the chronograph, for instance, is not as easy as with other Casio watches. That said while hiking at Lookout Mountain, all I wanted to know was what time is it, if a storm is coming, which direction am I facing, and what altitude am I at, and this did that with ease, even with a camera in one hand the entire time.

The solar-powered Japanese quartz movement is super accurate and ultra-reliable, however, while the self-powered movement is convenient, the lack of phone connectivity means the watch can operate without a phone, which means it’s both autonomous and lets you better connect with nature. You will have to set the time on this one yourself, which compared to a Bluetooth or Atomic radio-controlled timepiece, is an extra step, but it’s probably worth it considering it will still remain accurate to -/+15 seconds per month — and most importantly you can ditch the phone.

Retail is $280. Learn more at Casio.

Lookout Mountain Colorado peering East



Casio Protrek PRG-340-1

Reference: PRG-340-1

Year: 2022

Total Weight: 53.9 grams

Case Diameter: 51.7 mm

Case Thickness: 15.1 mm

Lug-to-lug: 54.7 mm

Crown Diameter: No crown

Lug Width: 23 mm (non-tapered resin strap)

Glass: Mineral crystal (armored)

Movement: Module 3513

Depth Rating: 100 meters

Power Reserve: 7 months (27 months if not being used and in power save mode)

Accuracy: -/+ 15 seconds per month

Posted by:Jason Pitsch

Jason is the founder of Professional Watches and specializes in writing, product photography, and digital marketing.