Casio · Pro Trek · Ref PRG-340-1
Fifty-four grams of sensor.
The lightest Triple Sensor Casio sells at this price, in a case moulded from bio-based resin. Module 3513 reads altitude to the metre every second, charges from light, and is rated to 100m. The compass is on the screen, not on a hand.
Module readout
01 /
Built from biomass
The PRG-340 replaced the PRG-240 in Casio’s line, and the case material changed with it. Casio moulds the case and band from bio-based resin, plastics made partly from renewable feedstock rather than entirely from petroleum.
The material is also light. At about 54 grams the PRG-340 is around 13 grams lighter than the PRG-270, on a footprint that is almost identical: 54.7mm long, 51.7mm wide, 15.1mm thick.
02 /
The compass on the bezel
The ring around the screen is printed with N, E, S and W and a full degree scale, with the N picked out in red. Press the sensor button, read the bearing on the LCD, then turn the watch until the number lines up with the letter. It is slower than a compass hand, and it is also unambiguous.
Altitude readings update every second in one-metre steps for up to a minute at a time, which makes a climb legible as it happens rather than as a summary afterwards. Pressure and temperature come from the same Triple Sensor Version 3 cluster.
03 /
The PRG-270 question
Both watches are all-digital solar Pro Treks with the same sensor suite and a 100m rating. The PRG-340 costs a little more, weighs less, uses the newer module and bio-resin, and has the more legible compass bezel.
Neither has radio timekeeping, Bluetooth, sapphire or a compass hand. If any of those matter, the answer is a PRW model, not a choice between these two.
Specs
- Reference
- PRG-340-1
- Case size
- 54.7 × 51.7 × 15.1mm
- Case material
- Bio-Based Resin
- Movement
- Tough Solar (Solar Quartz)
- Caliber type
- Tough Solar Quartz (No Battery Change)
- Crystal
- Mineral Glass
- Water resistance
- 100m (10 ATM)
- Power reserve
- Tough Solar (Rechargeable)
- Complications
- Triple Sensor (Compass, Altimeter/Barometer, Thermometer), Digital Display, Direction Bezel
- Origin
- Casio (Japan)
Specifications as published by Casio. We research from manufacturer documentation and published sources rather than hands-on testing. Researched 2026-09-03.
Verdict
The lightest Triple Sensor Pro Trek at its price, about 54 grams in bio-based resin, with metre-by-metre altitude readings and a red-N compass bezel.
Strengths
- About 54 grams, lighter than the PRG-270 on the same footprint
- Altitude in one-metre steps at one-second intervals
- Tough Solar charging with 100m water resistance
- Case and band moulded from bio-based resin
Trade-offs
- No radio or Bluetooth time sync
- Compass is read as a number on the screen, not pointed by a hand
- 51.7mm wide and 15.1mm thick
- Mineral glass rather than sapphire
Buy it if
Walkers and climbers who want frequent, precise sensor readings in the lightest package Casio offers at this price.
Skip it if
You want a hand that swings to north or a watch that sets itself. Casio’s analogue-display Pro Treks and the PRW-B1000 cover those.
FAQ
The PRG-340 uses bio-based resin for its case and band and a newer module, bringing it to about 54 grams against the PRG-270’s roughly 67 grams, on a nearly identical footprint.
Sources
- Casio Pro Trek PRG-340-1, Casio international product page
- Pro Trek PRG-340 release details, G-Central
Researched and last updated 2026-09-03. We do not test watches in hand; every figure above is traceable to the manufacturer or the sources listed here.
Casio Pro Trek PRG340-1
Reference PRG-340-1 · $150–$250
Prices and availability change; the band above is a research figure, so check the current listing.
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