Casio G-Shock GDF-100-1B Twin Sensor Watch

I have had many high speed watches in my day but this one is one of my favorites! Rugged, easy to use and just a great watch for anyone who works outdoors. Very accurate (you must know how to use a baromoter and understand that the temp will be higher than the actual temp when the watch is on your arm) and user friendly. The led light is BRIGHT! All in all, I really like this watch even when compared to my Suunto MI X9 ($500 watch).

Bought this for my son as a 14th birthday present at his request after much research on his part. I've had my original Cascio G-Shock since 1987, took it on all of my Airborne Infantry parachute and helicast ops, and been snorkelling with it, so he wanted one of his own. It is somewhat large - any bigger and he couldn't strap it on - but looks great and he loves it. The features are great with the following caveats: The face is intentionally "tactical". You cannot see the numbers unless in direct/day light. The backlight feature is very nice, though, and you can set how long it stays on. The temperature reads quite a bit high because the sensor is next to the skin (around 10 degrees high for my son), but is accurate if placed away from the body for a few minutes. Still testing the altimeter. We are going to Mexico soon, so we will test the multi-city time.The package came on time from the vendor without issue. The Amazon guarantee gave me the confidence to buy from an unknown seller.

As someone who regularly ventures into the wild outdoors, I needed a watch that would both durable and functional. This watch easily fulfills both needs. Out of the box, the sensors needed minimal calibration (which takes about 10 minutes). Like others have mentioned, the temperature readings will generally always be a little off while the watch is being worn. This is pretty unavoidable due to the timepiece's close proximity to the warmth that the human body gives off. Take the watch off your wrist for a couple minutes, and it seems to always be accurate within about 2 degrees. The included instruction manual reflects the same instruction.Despite the large size, the watch wears very well. It is not overly heavy, and the band is strong, while giving enough flexibility to to remain comfortable throughout the day. The finish to the band and bezel is a nice matte black that seems to resist scratches and dirt. The face is black with orange-red accents and numerical display. While it is not nearly as easily read in dark situations as the standard grey face/black lettering, it is really not that bad. I find that I can read it fairly easily in low light situations without resorting to using the light. As for the light itself, it is a bright blue that beautifully illuminates the watch face. The time the light remains on can be adjusted by the user (between 1 and 3 seconds), and is the perfect balance of making the text clear as day without being distractingly bright. The overall bulk of the watch is very manageable. It is worth noting that due to the thickness of the face, it can be awkward when wearing a shirt with tighter-fitting sleeves. However, this should be looked at as a timepiece for active people that can benefit from the durability. It is clearly not a dress watch, but that really should go without saying. Just for reference, I'm about 6'3", 200#, and fairly solid frame. The watch does not look huge on me, but rather quite fitting of someone my size.Pros:Great build quality and materials usedAccurate sensorsLightweight and strong, great for active lifestyles.Perfect level of illumination.Cons:Black face/orange lettering can occasionally be tough to read in the dark without using the light.Watch face is very thick, making it difficult to wear with shirts having tight fitting sleeves.

the light its not to the full screen, its like a cheap watch light.

Can't read it even in the daylight unless pressing the lighted dial button. Which, over time will reduce the battery life. The 100A is MUCH better,

its a g-shock: big, resistant, nothing to worry about. but the extras (thermometer, altimeter and barometer) are not reliable. the thermometer catches the heat of your body, so you need to take it out and wait to get a proper temperature. the altimeter and barometer go crazy all the time. it is a good watch for general use, but no good if you depend on the informations from the extras.

G-Shocks are fun watches to wear. What sets this model apart from a lot of G-Shocks is the somewhat offset dial. If you really want asymmetrical, go all out and get a Frogman. But I digress. This model comes loaded with the usual goodies from Casio: world time, stopwatch, countdown timer, and alarms. It also has sensors built in to show altitude, barometric pressure, and temperature. The negative / reverse dial is very unique, and I recommend seeing one in person before buying. It's really only visible in direct light, but the built in light does a fabulous job at lighting up the dial. And you can adjust the back light to last 1 or 3 seconds. Fit and finish is typical Casio fashion, and leaves little to be desired. Oh, and it's a big dial watch. Not obnoxious, just nice and chunky. Lightweight, too, so it sits comfortably on my wrist.

Durable and reliableLooks greatHad it for over a year and has given out yet. Haven't needed to replace batteries either.As far as the temp and height sensor I don't use it much but the height sensor seems pretty accurate.

Like the strap and features. The face is hard to read in daylight without turning on the backlight and using up the battery.

been using this virtually every day for 6 months and in pretty much all conditions. worked without flaw whilst being comfortable to wear. Only thing to bear in mind is that if you are or have been wearing the watch the temperature reading will be out until it has returned to ambient temperature, but this is to be expected really.