The daily alarm reminds you about recurring events with an acoustic signal at the time you have set. This model has 5 independent alarms for flexible reminders of important appointments.
Resin band
Synthetic resin is the ideal material for wrist straps thanks to its extremely durable and flexible properties.
Dual Illuminator
Both the digital and analogue areas of the watch face glow when the EL backlight is turned on.
Resin case
The case of the watch is light and durable.
Carbon-reinforced resin casing
Thanks to its extremely high level of durability, resin is the ideal material for watches. Combining resin with carbon—a particularly robust material—creates a casing that is even more stress-resistant and offers even greater protection against external influences, resulting in an extremely high level of durability.
Neo-display
A luminous coating provides long-term illumination in the dark after only a short exposure to light.
Mineral glass
The tough mineral glass resists damages.
Automatic calendar with Date, Day and Month
Once set, the automatic calendar always displays the correct date.
12/24-hour timekeeping
Times can be displayed in either a 12-hour or 24-hour format.
Hand Moving Function
With a push of a button, hands are moving and permit a free visibility of functions like stopwatch or date.
Shock-resistant
Shock-resistant construction protects against impact and vibration.
Water resistance classification (20 bar)
Perfect for free diving without scuba gear: the watch is water resistant up to 20 bar according to ISO 22810.
World time function
Displays the current time in major cities and specific areas around the world.
What’s in the box?
3-year warranty, extendable for another 3 years
User manual
Warranty card
CASIO G-SHOCK branded box
Reviews about G-SHOCK Octagon Casio Carbon Core Guard GA-2100-1AER (17)
The carbon-reinforced case makes a huge impression when it comes to this model’s durability in everyday situations. This design ensures exceptional resistance to all impacts and shocks, while the watch remains incredibly lightweight and practically imperceptible on the wrist when worn.
Erste
4/26/26
100%
I bought this watch for everyday use, and I have to admit that its biggest advantage is how incredibly slim and lightweight it is. Compared to other models in this series, the Octagon doesn’t stick out as much from the wrist, which makes it exceptionally comfortable and prevents it from catching on cuffs. The carbon-reinforced case gives a sense of sturdiness, even though the watch weighs very little. The matte finish looks modern and professional, and the controls are so simple that you don’t need to constantly consult the manual. It’s a great choice for anyone looking for rugged durability in a slightly more discreet, everyday design.
Samm
4/22/26
100%
I got this watch for my birthday. It’s sturdy and well-made. Japanese watches have an interesting history. It looks great on my wrist. I recommend it to everyone!
FarellJones
3/17/26
100%
What surprised me most was how light it is. Thanks to the carbon reinforcement, the watch is almost imperceptible on the wrist, yet you can tell it’s a sturdy piece of gear that can withstand quite a few knocks. The black, matte color scheme is very versatile—I wear it with both athletic wear and a plain sweatshirt, and it fits perfectly with everything. Even though the dial is analog-digital, reading the time is very intuitive. The Illuminator backlight works great at night, and the feature that moves the hands out of the way so they don’t block the small LCD screen is a very thoughtful detail. For someone just starting their journey with this brand, it’s the perfect entry-level model—iconic durability in a version that’s simply attractive and comfortable.
Coco
2/6/26
100%
Everything was as described, and delivery went smoothly.
Panikinalowa
1/1/26
100%
The watch meets my expectations thanks to its daily calendar, which makes planning much easier. The product is sturdy and well-made. The shopping experience at the store was quick and smooth. I highly recommend it!
kr00ps00n
12/30/25
100%
This model, with its reliable Japanese movement, meets my expectations. I also really appreciate the free engraving. The store processed my order efficiently.
Arczi
11/24/25
100%
The watch is very sturdy, and the durable plastic case fits comfortably on the wrist. The black color goes great with various outfits. I also appreciate that I found detailed photos on the website, which helped me choose the right model. The purchase went smoothly; I recommend this store.
Peony
11/17/25
100%
No complaints.
Norbertz.
10/11/24
100%
A modern design with clean, geometric lines. And that all-black look—it really makes an impression. It’s lightweight and well-made—it looks like it will be durable. Plus, it has bright backlighting, plenty of features, and a unique look.
DawidS
5/15/24
100%
I’m a big fan of G-SHOCK watches. I appreciate not only their durability and shock resistance, but also their unique design. This model is made of carbon fiber, making it extremely lightweight yet still resistant to impacts, scrapes, and other unexpected accidents. I lead an active lifestyle and don’t want to worry about whether I’ll damage my watch or if I can swim with it—with G-SHOCK, I can do so without worry, because it’s water-resistant up to 20 BAR. The ordering process itself went smoothly. I appreciate the fast shipping, the 100-day return policy, and the variety of payment options, including deferred and installment plans.
Jacob
3/3/24
80%
I am very happy with my purchase of the G-SHOCK watch. Its Japanese Casio 5611 quartz movement makes the watch incredibly precise and reliable. That’s crucial to me because I value punctuality. An added bonus was the wide range of payment methods available in the store, which made it easy for me to complete the purchase. The only downside was the longer wait time for delivery, which lowers my rating to 4 stars. Overall, though, I recommend it!
Alicja G.
10/2/23
100%
The Casio GA-2100 is a great men's watch. It features a stylish black design and a sturdy build. The Japanese quartz movement ensures precision. I highly recommend it!
Krzysztof
9/26/23
100%
The Casio GA-2100 men's watch is both sturdy and elegant. The Japanese quartz movement and black plastic case make for a perfect combination. The store staff were very helpful.
Tomasz
5/25/23
100%
Fast, efficient delivery. The watch is super durable and looks great on the wrist. It’s not too big and fits very comfortably.
Filip
4/26/23
100%
Nice model, very lightweight without any unnecessary embellishments
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The administrator of your personal data is the owner of the Watchard store, i.e. 57 Concepts Sp. z o.o. Sp. k. with the registered office at al. Witosa 31, lok. 115, 00-710 Warsaw, Poland. Providing personal data by the Customer is voluntary but necessary to complete the purchase. You have the right to view your personal data we have processed, as well as the right to request changes or removal of your personal data. Personal data will be processed for a period of 10 years.
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The administrator of your personal data is the owner of the Watchard store, i.e. 57 Concepts Sp. z o.o. Sp. k. with the registered office at al. Witosa 31, lok. 115, 00-710 Warsaw, Poland. Providing personal data by the Customer is voluntary but necessary to complete the purchase. You have the right to view your personal data we have processed, as well as the right to request changes or removal of your personal data. Personal data will be processed for a period of 10 years.
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