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Casio G-Shock GA-2100-1A1ER: The ‘CasiOak’ Everyone Actually Means When They Say That

The watch GQ called ‘Cool AF’ and that sold out globally for months. Real reviews, one honest recurring complaint, and the price in Ireland.

Casio G-Shock GA-2100-1A1ER: The 'CasiOak' Everyone Actually Means When They Say That

The Casio G-Shock GA-2100-1A1ER is a 45.4mm analog-digital watch with an octagonal case, nicknamed the 'CasiOak' for its resemblance to the Audemars Piguet Royal Oak, currently €89.95 on Amazon.ie.

This is one of the most independently reviewed watches on this site to date, multiple dedicated watch outlets (Scottish Watches, Quill and Pad, Ben’s Watch Club, WatchCrunch, Millenary Watches) have covered this exact reference in depth, and they largely agree with each other, including on its one real weakness. This review is built from that body of independent testing rather than a hands-on unit at menswatches.ie. For similar watches, visit Casio Watches for Men.

In this review
  • Why it's called the CasiOak, and why that mattered commercially
  • What multiple independent reviewers agree on, praise and complaint alike
  • The real case size versus how it actually wears
  • What 200m water resistance genuinely covers
  • Price €89.95 on Amazon.ie, down from €99.90, sold and shipped by Amazon.ie directly.
  • The nickname is a real phenomenon Multiple outlets independently confirm this watch sold out globally for months after its 2019 launch and was called ‘Cool AF’ by British GQ, genuine mainstream crossover attention, not marketing language.
  • Case size is bigger on paper than in practice 45.4mm diameter sounds large, but independent reviewers consistently note the shorter lug-to-lug and integrated bracelet make it wear closer to a 42mm watch.
  • One recurring complaint Multiple independent reviewers separately flag the same issue: the negative display is genuinely hard to read without direct light, the dark hands blend into the dial.
What independent reviewers agree on, good and bad

This is unusually well documented for a watch at this price. Scottish Watches, WatchCrunch, Millenary Watches and Watch Clicker have all reviewed this exact reference independently, and the overlap in their findings is the real signal here. On the case: multiple reviewers separately measured or cited 45.4mm diameter and roughly 11.8mm thickness, making it, by Casio’s own claim, the thinnest G-Shock ever produced. On wearability: several reviewers who initially found the diameter intimidating reported it wearing smaller than expected, one specifically noted no issues on a 6.5 inch wrist despite the number on paper.

On the downside, the same complaint shows up independently across multiple reviews: the negative display (dark background, light digits) is genuinely difficult to read without direct light, and the neobrite hands can blend into the dark dial. That’s not one reviewer’s bad unit, it’s a consistent design tradeoff worth knowing before buying.

Casio G-Shock GA-2100-1A1ER
200m water resistant Wears smaller than its size Legibility is the trade-off

A genuine cult watch with the independent review coverage to back that up, not just internet hype. The design, comfort and durability claims are consistently confirmed across multiple dedicated reviewers. The one honest trade-off, legibility without direct light, shows up repeatedly enough across independent sources to take seriously, but it doesn’t come close to outweighing what this gets right at the price.

Check price on Amazon.ie
Key specs
45.4mm
Case diameter
11.8mm
Case thickness
Approximately 47 to 48.5mm depending on source
Lug-to-lug
Resin with Carbon Core Guard construction
Case material
Mineral
Crystal
Quartz, module 5611
Movement
200m (20 bar)
Water resistance
World time, 1/100 second stopwatch, countdown timer, 5 alarms, auto calendar to 2099, LED backlight
Functions
Approximately 3 years
Battery life
51 to 52g
Weight
Resin, 24mm width
Strap
Best for
Buyers who want a genuinely well-reviewed, design-led G-Shock, not just a functional one Anyone comfortable checking the time in decent light rather than pitch darkness
Not for
Buyers who need to read the time reliably in low light without pressing the backlight Anyone wanting the smallest possible case diameter
Pros
  • Genuine cult following backed by real independent review coverage, not just online hype
  • Consistently described as the thinnest G-Shock ever made, genuinely comfortable despite the diameter
  • 200m water resistance and Carbon Core Guard durability are real, well-documented specs
  • Multiple reviewers confirm it wears smaller than its 45.4mm diameter suggests, thanks to the lug-to-lug and integrated bracelet
Cons
  • Multiple independent reviewers separately flag the same issue: hard to read without direct light
  • 45.4mm is a genuinely large diameter on paper, even if it wears smaller
  • Mineral crystal rather than sapphire
  • High demand has meant this exact model has been difficult to find in stock at points since launch
8.5
10
Design 9.5
Comfort 8.5
Value 9.0
Legibility 6.0
Where to buy

Where to Buy

Offers: 1 Updated: 15 hours ago
€99.90 €94.79
in stock
Frequently Asked Questions
Why is it called the CasiOak?

Its octagonal bezel and integrated bracelet closely resemble the Audemars Piguet Royal Oak. The nickname originated in watch forums and stuck, and the watch went on to sell out globally for months after its 2019 launch.

Is 45.4mm too big for a smaller wrist?

Multiple independent reviewers report it wears smaller than the number suggests, thanks to a relatively short lug-to-lug and the integrated bracelet design. One reviewer specifically had no issues on a 6.5 inch wrist.

Is it hard to read the time?

In low light, yes, this is a consistent, independently repeated complaint. The negative display and dark hands against a dark dial make it genuinely difficult to read without direct light or the backlight.

Can you swim or dive with it?

Yes, it’s rated 200m, which independent reviewers describe as suitable for both swimming and recreational diving.

Conclusion
  • Independently reviewed by multiple dedicated watch outlets reaching the same conclusions
  • One real, repeated complaint on legibility in low light; everything else holds up consistently

This is a rare case of internet hype actually holding up under scrutiny. Multiple independent, dedicated watch reviewers reached the same conclusions separately: genuinely comfortable despite a large-sounding case, genuinely durable, and genuinely let down by one specific, repeated flaw, legibility without direct light. That’s a real, evidenced trade-off rather than a manufactured criticism for balance. At €89.95, the positives independent reviewers keep confirming outweigh the one honest complaint.