Casio G-Shock GA-2100 CasiOak: The Complete Australia Guide (2026)
Casio G-Shock GA-2100 CasiOak: The Complete Australia Guide (2026)
Watch Guide · 2026 · 9 min read · WatchDirect Team
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The Audemars Piguet Royal Oak costs around $30,000. The GA-2100 costs $279. Both wear an octagonal bezel, both look immediately recognisable on the wrist — and somewhere between 2019 and now, the internet decided to call Casio's version the "CasiOak." It's a joke that became a compliment. And for good reason.
Casio didn't design the GA-2100 to chase AP. The octagonal shape came from a structural decision — Carbon Core Guard architecture, a carbon-reinforced resin case that lets the watch slim down to 11.8mm, one of the thinnest G-Shock ever made. The Royal Oak comparison was a happy accident. But it stuck, because the GA-2100 genuinely looks better than a watch at this price has any right to.
Five years after launch, the CasiOak lineup has expanded from a single black model to a family of more than a dozen variants — Bluetooth, solar, steel, women's sizing, transparent casings. This guide covers the GA-2100 range, what separates each model, and which is right for your wrist.
At a Glance
- Best entry-level CasiOak: GA2100-1A — all-black, full spec, nothing to overthink
- Best for Bluetooth + Solar: GAB2100-1A — set-and-forget timekeeping, no battery swaps ever
- Best colourway: GA2100AS-2A — navy blue that reads totally differently in sun vs shade
- Best for women: GMAP2100-7A — smaller GMA case, same CasiOak DNA
- Best statement piece: GM2100RW-1A — stainless steel bezel, serious presence
- Best conversation starter: GA2100BM-7A5 — transparent casing that shows its own skeleton
- Best for minimalists: GMAP2100ST-9A — beige on beige, soft and considered
- Best versatile solar pick: GAB2100LUU-5A — grey dial, white band, everyday wearability
In This Guide
- The CasiOak Story
- What Makes the GA-2100 Different
- The GA-2100 Range
- GA-2100 Series Comparison Table
- Which CasiOak Is Right for You?
- FAQ
- Customer Experiences
The CasiOak Story
The GA-2100 launched in 2019. Casio didn't announce it with fanfare — it was a quiet addition to the G-Shock lineup, notable mostly for being unusually thin. Twelve millimetres. For context, most G-Shocks sit around 15–18mm thick. The GA-2100 felt almost unreal on the wrist.
Then watch forums noticed the bezel. Eight sides. The octagonal shape, combined with the clean dial layout and flat profile, reminded people of the Royal Oak — Gerald Genta's 1972 design for Audemars Piguet that redefined what a luxury sports watch could look like. Someone called it a "CasiOak" and the name never left.
What made it resonate wasn't just the shape. It's that the GA-2100 earned the comparison on aesthetic terms. The dial is restrained. The bezel is purposeful. Nothing shouts. For a watch that costs $279, it reads as designed — not assembled.
By 2020 it was one of G-Shock's best-sellers globally. Casio responded the only way it could: more colourways, GAB variants with Bluetooth and solar, the GM line with a steel bezel, and women's sizing under the GMA-P2100 prefix. The nickname followed them all.
What Makes the GA-2100 Different
Carbon Core Guard. This is the engineering story behind the thinness. Traditional G-Shock cases wrap components in thick resin to absorb shock. Carbon Core Guard uses a carbon-fibre reinforced inner frame, which is significantly stronger per millimetre than standard resin. The result is a case that offers full G-Shock protection — 200m water resistance, genuine shock resistance — in a profile that actually fits under a shirt cuff.
The analog-digital combo. Most G-Shocks lean one way or the other. The GA-2100 blends both without looking cluttered. A clean analog face with sword hands dominates the upper dial. A small digital window sits below, handling world time, stopwatch, and alarms. You read the time from the hands. You configure everything else from the display. It works.
The hand shift feature. This is a small detail that matters more than it sounds. When you use the digital functions, the analog hands automatically park out of the way so they don't obscure the display. When you're done, they return to the correct time. It's a small detail you notice in the first week and never stop appreciating.
Wearability. G-Shock has always been a big watch proposition. The GA-2100 breaks that pattern. At 51 grams and 11.8mm thin, it wears closer to a dress watch than a tool watch. People who'd written off G-Shock as too bulky tend to reconsider. That's the real achievement here.
The GA-2100 Range
Casio G-Shock GA-2100-1A
G-Shock · CasiOak · Everyday Wear
This is where the CasiOak story started. All-black resin band, black dial, black carbon case — it's monotone in the best way. The dial is clean enough that people regularly assume it's more expensive than it is, and the 11.8mm thickness means it disappears under a jacket sleeve in a way most G-Shocks never could.
There's nothing tricky about the GA2100-1A. No solar, no Bluetooth, no frills. Just the Carbon Core Guard case, 200m water resistance, a world time function covering 48 cities, and a Super Illuminator backlight that actually lights the entire dial. If you want the purest version of the CasiOak, this is it.
- Movement: Quartz analog-digital, ±15 sec/month
- Case: Carbon Core Guard resin, 48.5 × 45.4 × 11.8mm, 51g
- Water resistance: 200m
- Features: World time (48 cities), stopwatch, countdown timer, 5 alarms, hand shift, Super Illuminator
- Price (RRP): $279 AUD
Casio G-Shock GA-2100-1A1
G-Shock · CasiOak · Everyday / Dress Casual
The 1A1 sits right next to the 1A in the lineup, and on first glance they look like the same watch. Look closer. The white index markings and hour hand tip give this version a slightly more technical feel — closer in spirit to a tool watch dial than straight stealth-black. Small difference. Real difference.
Same Carbon Core Guard case, same 11.8mm profile, same full G-Shock spec. The choice between 1A and 1A1 is purely aesthetic — and that's a good problem to have at $279. Both wear identically.
- Movement: Quartz analog-digital, ±15 sec/month
- Case: Carbon Core Guard resin, 48.5 × 45.4 × 11.8mm, 51g
- Water resistance: 200m
- Features: World time (48 cities), stopwatch, countdown timer, 5 alarms, hand shift, Super Illuminator
- Price (RRP): $279 AUD
Casio G-Shock GAB-2100-1A
G-Shock · CasiOak Solar Bluetooth · Travel / Tech
The GAB-2100 is the CasiOak grown up. Bluetooth connects to the G-Shock Connected app on your phone, which syncs the time automatically — time zone changes, daylight saving, all handled. Pair that with Tough Solar charging (any light source charges the capacitor, no battery replacement ever) and you have a watch you never have to maintain.
The extra $50 over the standard GA-2100 is genuinely worth it for frequent travellers. Land in Tokyo, pull your phone out of flight mode, and your watch has already corrected itself. The all-black colourway keeps this feeling as clean as the base model.
- Movement: Quartz analog-digital with Bluetooth, ±15 sec/month (synced via app)
- Case: Carbon Core Guard resin, 48.5 × 45.4 × 11.8mm, 51g
- Water resistance: 200m
- Features: Bluetooth 5.0, Tough Solar, world time (48 cities), stopwatch, 5 alarms, hand shift, Super Illuminator
- Price (RRP): $329 AUD
Casio G-Shock GAB-2100-1A1
G-Shock · CasiOak Solar Bluetooth · Travel / Everyday
Functionally identical to the GAB2100-1A — Bluetooth sync, Tough Solar, the works. The 1A1 adds white dial markings and a contrasting hour hand tip, which makes the time easier to read at a glance. If you're going to be checking this watch in meetings or dim environments, that contrast matters.
Like the standard 1A, this is a watch you charge by existing — just wear it outdoors occasionally and the solar capacitor stays topped up. The Bluetooth connection via the G-Shock Connected app handles everything else.
- Movement: Quartz analog-digital with Bluetooth, ±15 sec/month (synced via app)
- Case: Carbon Core Guard resin, 48.5 × 45.4 × 11.8mm, 51g
- Water resistance: 200m
- Features: Bluetooth 5.0, Tough Solar, world time (48 cities), stopwatch, 5 alarms, hand shift, Super Illuminator
- Price (RRP): $329 AUD
Casio G-Shock GAB-2100LUU-5A
G-Shock · CasiOak Solar Bluetooth · Lifestyle / Sport
Grey dial, white resin band. It's a simple combination that works harder than it looks. The LUU-5A breaks from the monochromatic approach of earlier CasiOaks — it's more relaxed, more lifestyle than tactical, and it works across a wider range of outfits than you'd expect.
Under the hood it's still a full GAB — Bluetooth, Tough Solar, 200m water resistance. You get all the practical advantages of the smarter CasiOak variants dressed in a colourway that genuinely suits summer in Australia.
- Movement: Quartz analog-digital with Bluetooth, ±15 sec/month (synced via app)
- Case: Carbon Core Guard resin, 48.5 × 45.4 × 11.8mm, 51g
- Water resistance: 200m
- Features: Bluetooth 5.0, Tough Solar, world time (48 cities), stopwatch, 5 alarms, hand shift, Super Illuminator
- Price (RRP): $329 AUD
Casio G-Shock GA-2100AS-2A
G-Shock · CasiOak · Everyday / Casual Sport
Navy watches are having a moment and the GA2100AS-2A earns its place in that conversation. The blue dial and matching navy band have a depth to them that shifts depending on the light — indoors it reads dark and serious, outdoors in direct sun it opens up and shows character. The octagonal bezel in navy particularly recalls the Royal Oak connection; the blue is a reference colourway for AP's icon.
At $299, the AS-2A sits between the base black models and the solar GAB variants. Same Carbon Core Guard case, same 200m water resistance, same full G-Shock functionality. The premium here is purely colourway — and it's worth it.
- Movement: Quartz analog-digital, ±15 sec/month
- Case: Carbon Core Guard resin, 48.5 × 45.4 × 11.8mm, 51g
- Water resistance: 200m
- Features: World time (48 cities), stopwatch, countdown timer, 5 alarms, hand shift, Super Illuminator
- Price (RRP): $299 AUD
Casio G-Shock GMA-P2100-7A
G-Shock S Series · CasiOak Women's · Lifestyle / Active
The GMA-P2100 is the women's CasiOak — a proportionally scaled version of the GA-2100 that fits smaller wrists without sacrificing any of the design language. This all-white version is clean, striking, and completely unafraid of itself. It's the kind of watch that pairs equally well with a sundress and with gym gear.
G-Shock's "mini" women's watches often get written off as toys. This one doesn't deserve that. The octagonal bezel is still present, the white dial is genuinely legible, and the full G-Shock spec — including 200m water resistance — is all there. At $259, it's the most affordable CasiOak in the range.
- Movement: Quartz analog-digital, ±15 sec/month
- Case: Carbon Core Guard resin (GMA proportional sizing), resin band
- Water resistance: 200m
- Features: World time (48 cities), stopwatch, countdown timer, 5 alarms, Super Illuminator
- Price (RRP): $259 AUD
Casio G-Shock GM-2100RW-1A
G-Shock G-Steel · CasiOak Premium · Dress Sport / Statement
The GM-2100 takes everything that works about the CasiOak and wraps the octagonal bezel in stainless steel. On the wrist, it doesn't just look different — it feels different. The heft of the steel bezel against the lightweight resin case is an unusual combination that somehow works. It wears like a G-Shock but glances like something from a different category entirely.
At $549, the GM2100RW-1A is the premium end of the CasiOak family. The steel bezel and finishing justify the step up. If you want the most substantial version of this watch, this is it.
- Movement: Quartz analog-digital, ±15 sec/month
- Case: Carbon Core Guard resin with stainless steel bezel, 48.5 × 45.4 × 11.8mm
- Water resistance: 200m
- Features: World time (48 cities), stopwatch, countdown timer, 5 alarms, hand shift, Super Illuminator
- Price (RRP): $549 AUD
Casio G-Shock GA-2100BM-7A5
G-Shock · CasiOak Transparent · Streetwear / Statement
The BM-7A5 is the CasiOak you wear when you're done being subtle. Transparent resin — case and band — exposes the internal structure, the components, the layout that sits underneath every other GA-2100. What's usually hidden is the whole point here. Not everyone's thing. But for some people, it's the only CasiOak that makes sense.
Functionally it's identical to the base GA-2100 — no solar, no Bluetooth, just the full standard spec at $299. The transparent finish is the point here, and Casio has executed it well. This doesn't look cheap or gimmicky. It looks intentional.
- Movement: Quartz analog-digital, ±15 sec/month
- Case: Transparent Carbon Core Guard resin, 48.5 × 45.4 × 11.8mm, 51g
- Water resistance: 200m
- Features: World time (48 cities), stopwatch, countdown timer, 5 alarms, hand shift, Super Illuminator
- Price (RRP): $299 AUD
Casio G-Shock GMA-P2100ST-9A
G-Shock S Series · CasiOak Women's · Lifestyle / Minimalist
Neutral colourways are hard to get right — too warm and they look dated, too cool and they lose character. The GMA-P2100ST-9A lands it. Beige dial, beige band, markers that don't shout. It barely announces itself, and that's the whole idea.
Like the all-white 7A, this is the women's GMA case — proportionally sized for smaller wrists while keeping the octagonal CasiOak shape intact. Full G-Shock spec underneath the soft exterior. $279 for a women's watch this considered is not a question.
- Movement: Quartz analog-digital, ±15 sec/month
- Case: Carbon Core Guard resin (GMA proportional sizing), beige resin band
- Water resistance: 200m
- Features: World time (48 cities), stopwatch, countdown timer, 5 alarms, Super Illuminator
- Price (RRP): $279 AUD
GA-2100 Series Comparison Table
| Model | RRP (AUD) | Solar | Bluetooth | Bezel | Colourway | Case |
|---|---|---|---|---|---|---|
| GA2100-1A | $279 | — | — | Resin | All Black | GA (men's) |
| GA2100-1A1 | $279 | — | — | Resin | Black / White accents | GA (men's) |
| GA2100AS-2A | $299 | — | — | Resin | Blue / Navy | GA (men's) |
| GA2100BM-7A5 | $299 | — | — | Transparent Resin | Clear / Skeleton | GA (men's) |
| GAB2100-1A | $329 | ✓ Tough Solar | ✓ BT 5.0 | Resin | All Black | GA (men's) |
| GAB2100-1A1 | $329 | ✓ Tough Solar | ✓ BT 5.0 | Resin | Black / White accents | GA (men's) |
| GAB2100LUU-5A | $329 | ✓ Tough Solar | ✓ BT 5.0 | Resin | Grey Dial / White Band | GA (men's) |
| GM2100RW-1A | $549 | — | — | Stainless Steel | Black / Steel | GA (men's) |
| GMAP2100-7A | $259 | — | — | Resin | All White | GMA (women's) |
| GMAP2100ST-9A | $279 | — | — | Resin | Beige / Cream | GMA (women's) |
Which CasiOak Is Right for You?
The GA-2100 family is genuinely well segmented. The decision tree is shorter than it looks:
→ "I want the classic, done."
Go with the GA2100-1A. It's the original. Nothing is missing.
→ "I travel a lot and hate fussing with watch settings."
The GAB2100-1A or GAB2100-1A1 solves that completely. Bluetooth auto-sync, solar charging — it just works.
→ "I want colour, not just black."
The GA2100AS-2A (navy) is the strongest non-black option in the range. The GAB2100LUU-5A (grey/white) is also worth considering if solar is important.
→ "I want the nicest version, money isn't the main concern."
The GM2100RW-1A. The stainless steel bezel changes everything — this is the CasiOak that punches hardest above its weight.
→ "I want something for a smaller wrist / buying for a woman."
The GMAP2100-7A (white) or GMAP2100ST-9A (beige) are the women's GMA case — proportionally scaled, same DNA.
→ "I want to be the only person in the room wearing this."
The GA2100BM-7A5 transparent. No further questions.
Frequently Asked Questions
What does "CasiOak" mean?
It's a portmanteau of Casio and Royal Oak — the iconic watch by Audemars Piguet designed by Gerald Genta in 1972. The GA-2100's octagonal bezel drew comparisons from watch enthusiasts online, the nickname stuck, and Casio eventually leaned into it. It's now how most people refer to the GA-2100 series.
How waterproof is the GA-2100?
200 metres. That's the same rating as most serious dive watches, and far more than you'll ever need for swimming, surfing, snorkelling, or anything short of scuba diving. You can wear this in the ocean without a second thought.
How thin is the GA-2100 compared to other G-Shocks?
At 11.8mm, the GA-2100 is one of the thinnest G-Shock watches ever made. Most G-Shocks run 15–18mm thick. The difference is immediately noticeable — the GA-2100 actually fits under a shirt cuff, which most G-Shocks don't manage.
What's the difference between GA-2100 and GAB-2100?
The GAB-2100 adds Bluetooth connectivity and Tough Solar charging to the standard GA-2100 platform. Bluetooth lets the watch sync time automatically via the G-Shock Connected app on your phone — time zone changes and daylight saving handled without manual input. Tough Solar means the watch charges from any light source, so you never replace the battery. The RRP difference is $50.
Does the GA-2100 need a battery replacement?
The standard GA-2100 runs on SR726W batteries — rated at 3 years, though real-world life often exceeds that. The GAB-2100 uses Tough Solar and doesn't need battery replacement at all; light exposure keeps the capacitor charged indefinitely.
What's Carbon Core Guard and why does it matter?
Carbon Core Guard is Casio's engineering solution for making G-Shock thinner without sacrificing protection. An inner frame made from carbon-fibre reinforced resin provides rigidity and shock absorption while taking up significantly less space than traditional thick resin construction. The result is a G-Shock that legitimately fits into thinner watch territory without compromising durability.
What's the difference between the GA-2100 and GM-2100?
The GM-2100 replaces the resin octagonal bezel with a stainless steel bezel. Everything else — the case dimensions, the movement, the feature set — remains the same. The steel bezel adds visual weight and a more premium feel, and it's reflected in the higher RRP ($549 vs $279).
Is the GA-2100 good for everyday wear?
It's one of the best G-Shocks for everyday wear, specifically because of the thinness. At 51g and 11.8mm, it doesn't feel like you're wearing a watch — it just sits on the wrist. Full G-Shock protection means you don't have to baby it, and the design is clean enough to move between casual and smart-casual outfits without looking out of place.
What's the difference between GMA-P2100 and GA-2100?
The GMA-P2100 is the women's proportioned version of the CasiOak. The case is slightly smaller to fit narrower wrists, but the octagonal bezel design, Carbon Core Guard construction, and core G-Shock features remain consistent. The GMA models carry a lower RRP starting at $259.
Is WatchDirect an authorised Casio dealer in Australia?
Yes. WatchDirect is an authorised Australian Casio and G-Shock retailer, trusted by Australians since 2011. Every G-Shock sold through WatchDirect comes with the full Australian manufacturer's warranty. You're not buying grey-market.
What Our Customers Say
"I was sceptical about the Royal Oak comparison — seemed like hype. Then I put the GA2100-1A on my wrist. The thing is genuinely good-looking. Clean, flat, just sits there. I've had mine six months and still reach for it first every morning."
— James K., Sydney · GA-2100-1A
"Got the GAB2100-1A for a trip through Southeast Asia. Set it once, the app handled every time zone change for two weeks. The solar keeps it charged — genuinely didn't think about the watch once the whole trip. That's the highest compliment I can give a travel watch."
— Marcus T., Melbourne · GAB-2100-1A
"Bought the GMA-P2100ST-9A in beige and I love how understated it is. Everyone else at work has flashy colourways — this one just looks… considered. Fits perfectly on my wrist. Waterproof enough for the beach. Couldn't ask for more at this price."
— Priya N., Brisbane · GMA-P2100ST-9A
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