A light-emitting diode (LED) is used to illuminate the watch face.
Shock-resistant
Shock-resistant construction protects against impact and vibration.
Neo-display
A luminous coating provides long-term illumination in the dark after only a short exposure to light.
World time function
Displays the current time in major cities and specific areas around the world.
Stopwatch function - 1/100 sec. - 24 hours
Accuracy of measurement up to 1/100 of a second, measuring range up to 24 hours.
Timer - 1/1 sec. - 24 hours
For fans of precision: the countdown timers help you to remember specific or recurring events by giving off an audible signal at a preset time. They The time can be set to the nearest second and up to 24 hours in advance.
5 daily alarms
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.
Button tones on/off
The button tones for using the mode button can be turned off. This means that the watch no longer beeps when switching from one function to another. Preset alarm or countdown timers remain active when the button tones are deactivated.
Hand Moving Function
With a push of a button, hands are moving and permit a free visibility of functions like stopwatch or date.
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.
Mineral glass
The tough mineral glass resists damages.
Folding clasp
The watch has a folding clasp.
3 Years - 1 Battery
The battery supplies the watch with sufficient energy for approx. three years.
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.
What’s in the box?
3-year warranty
User manual
Warranty card
Casio box
Reviews about G-SHOCK Octagon Classic Tone on Tone Carbon Core Guard GA-2100-9A9ER (6)
I received the watch as a gift. The product matches the photos on the website. I'm very happy with it.
Mas
3/8/26
100%
I bought this watch for myself. I really like its modern style. I'm happy with my choice.
Szczepan
2/4/26
100%
This yellow G-SHOCK is a real showstopper for anyone who wants to stand out from the crowd. The Tone on Tone version from the Octagon collection looks incredibly fresh and energetic, and this intense color makes the watch the focal point of any casual outfit. Despite its lightness and slim case—a rarity in this product family—it still features Carbon Core Guard technology, so durability is a given. I really like that the dial is easy to read, and the Neobrite coating on the hands lets you quickly check the time, even in total darkness. The water resistance rating of up to 200 meters gives me a sense of security while swimming or on vacation adventures, and the shock-resistant construction makes this a virtually indestructible piece of gear. The world time function and automatic calendar, in turn, are great conveniences for frequent travelers. It’s simply the perfect blend of iconic design and a modern, bold color that lifts my spirits every time I put it on my wrist.
Torpediusz
1/7/26
100%
I recently bought this watch model and I’m very happy with my choice. The quartz movement is precise, and the battery life—which is supposed to last three years—is a big plus. The watch is comfortable and fits perfectly on the wrist. I also appreciate the free, custom engraving, which added a personal touch to this purchase. The ordering process itself went smoothly, and delivery was fast and hassle-free. The store’s staff deserves praise for their professionalism and courtesy. Overall, I recommend this store and product to anyone who values quality and reliability. I feel that this watch meets all my expectations and will serve me well for a long time. It’s definitely worth it!
Karmel
11/25/25
100%
I recently bought this model and I’m really happy with it. The watch is sturdy, and the quartz movement with a 3-year battery life works great. I appreciate the Japanese precision, which ensures accuracy and reliability. Wearing it every day is a pleasure because it’s lightweight and comfortable. The store’s service was efficient and hassle-free, and the shipment arrived on time. The watch meets my expectations and looks great. I recommend it to anyone looking for a durable and functional timepiece.
Bułkowski
11/17/25
100%
The watch looks great and works well for everyday use. It’s sturdy and durable. Plus, I’m glad the shipping was free and fast. I’m very happy with my purchase and would recommend this store.
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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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