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The Casio G-Shock GA2100-1A is a strong everyday choice if you want a slim, light analog-digital watch with 200-meter water resistance and practical timing features. It measures 48.5 × 45.4 × 11.8 mm and weighs 51 g, but it runs on replaceable batteries rather than solar power and has no Bluetooth. Casio introduced the 2100 series in 2019, so “review of 2021” is not its launch date.
What the GA2100-1A is—and what it is not
The GA2100-1A is the black resin-and-carbon model in Casio’s G-Shock 2100 series. “CasiOak” is an informal nickname; the manufacturer’s model name is GA2100-1A. Casio says the 2100 series was introduced in 2019, not 2021. Casio’s U.S. product page lists the exact model and its specifications.
| # | Preview | Product | Price | |
|---|---|---|---|---|
| 1 |
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G-Shock GA-2100-1A1 Black One Size | $92.95 | Buy on Amazon |
| 2 |
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G-Shock GA2100VB-1A Black One Size | $104.69 | Buy on Amazon |
Be careful with similar model numbers. The GA-2100-1A1 is a separate lookalike, while GAB2100 models add Tough Solar power and Bluetooth. GM2100 variants use metal elements and differ in finish and specifications. Those features are not part of the base GA2100-1A.
Size, weight, and materials
The case measures 48.5 mm from top to bottom, 45.4 mm across, and 11.8 mm thick. Its listed weight is 51 g. The case and bezel use carbon/resin construction with Casio’s Carbon Core Guard structure, and the band is resin. The glass is mineral. These figures make the watch relatively thin for the 2100 line, but its nearly 49 mm case length is still important when judging wrist fit.
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- The rugged watch's 45.4mm case is expertly crafted from fine resin mixed with carbon fiber, an innovative composition that is lighter and more durable than resin
- The smooth black dial features an analog-digital display and double LED light feature, for easy visibility in the dark
Casio describes the 11.8 mm profile as making the 2100 series a comfortable everyday watch. That is the manufacturer’s product-page description, not a guarantee of fit for every wrist. Casio Europe lists a compatible band-size range of 145 to 215 mm; that measurement does not confirm that every aftermarket strap or conversion kit will fit. Casio Europe’s product page lists the band-size range and specifications.
Features and everyday use
The GA2100-1A combines analog hands with a digital display. Its listed functions cover common timekeeping needs rather than smartphone-connected tracking or advanced training features.
- World time covering 31 time zones, with 48 cities plus UTC
- 1/100-second stopwatch and 24-hour countdown timer
- Five daily alarms
- Double LED illumination
- Full auto-calendar through 2099
- Hand shift, which moves the hands out of the way of the digital display
- Manufacturer-stated accuracy of ±15 seconds per month
Casio specifies 200-meter water resistance (20 bar). The rating and G-Shock construction make this a practical option for active daily wear, but they do not make the watch a substitute for checking activity-specific guidance or care instructions.
Battery life: no solar charging on this model
The GA2100-1A uses two SR726W batteries. Casio estimates approximately three years of battery life; this is the manufacturer’s estimate, not a guaranteed replacement interval. The base model does not have solar charging. If avoiding routine battery replacement matters, compare it with a solar-powered GAB2100 instead.
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- The classic Casio G-Shock analog-digital watch takes a dive into the world of virtual reality with this Virtual World style
- The basic black coloring of the watch is accented by blue violet, which creates a futuristic atmosphere of virtual reality that pairs well with this model's octagonal bezel.Case/bezel material: Carbon/ResinBlack Resin BandMineral GlassShock ResistantCarbon Core Guard structure200-meter water resistanceDouble LED lightLED light for the face (Super illuminator, selectable illumination duration (1.5 seconds or 3 seconds), afterglow)LED backlight for the digital display (Super illuminator,
How it compares with other 2100 models
Casio USA’s comparison panel, accessed in 2026, lists these U.S. prices. They are current listed prices at that time, not historical 2021 prices, and can change; availability and pricing may differ by region.
| Model | U.S. listed price | Key distinction |
|---|---|---|
| GA2100-1A | $110 | Base carbon/resin analog-digital model; standard battery power and no Bluetooth |
| GAB2100-1A | $165 | Adds Tough Solar power and Bluetooth |
| GM2100-1A | $220 | Metal-look variant; materials and specifications differ from the base model |
| GMB2100D-1A | $600 | Metal variant with differences in materials, size, weight, or connectivity |
Prices and the broad variant distinctions above come from Casio USA’s comparison panel. Check the specific model’s current local listing before buying: a similar silhouette does not mean identical power, connectivity, materials, size, or weight.
Is the GA2100-1A worth buying?
It is worth considering if you want a relatively slim G-Shock with analog and digital timekeeping, a lightweight resin band, core timer and alarm functions, and substantial water resistance. Its most important trade-off is straightforward: the base GA2100-1A is less connected and requires battery replacement, unlike the solar/Bluetooth GAB2100. Its dimensions—not thickness alone—should also guide your decision, particularly if you prefer a smaller watch.
Casio USA lists the GA2100-1A at $110 in 2026. That is a current U.S. list price, not a 2021 price or a promise of the price you will find locally. Compare the exact suffix and features when weighing it against another 2100 model.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
