Casio G-Shock GA-2100-1AER review
The everyday G-Shock to start with: thin for the range, tough and easy to read.
- Skip it if
- You want a watch that never needs a battery
as of 6 Nov 2026, 13:25 GMT · Details
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Researched, not used. We haven't used this product. This review is built from the maker's details and what other buyers report.
What we like
- Slim octagonal CasiOak shape
- Analogue hands with a small digital display
- Carbon-reinforced resin case
Worth knowing
- Quartz rather than solar
- Case is wider than the slimness suggests
- Battery lasts only a few years
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Our review
The GA-2100-1AER is the slim octagonal G-Shock that has become the most recognisable watch in the range, nicknamed the CasiOak for its resemblance to a famous steel sports watch. It combines analogue hands with a small digital display in a carbon-reinforced resin case. It runs on a battery that lasts a few years. The trade-offs are that it is quartz rather than solar and the case is wider than the slimness suggests.
What it is
The GA-2100 launched as a thinner, simpler take on the usual large G-Shock, and the black 1A version is the base model. The octagonal bezel and the stripped-back dial helped it break out beyond the usual G-Shock audience. Within the range it sits below the solar and Bluetooth GA-B2100 and well above the plain DW-5600 digitals in complexity.
The movement
It uses a quartz module with analogue hands and a small digital readout of the date and extra functions. Casio quotes battery life of about three years, and the cell is replaceable. Accuracy is about 15 seconds a month either way. There is no solar charging, no radio sync and no Bluetooth on this reference, so if you want those look elsewhere. Functions include world time, stopwatch, timer and alarm, and the interface is easy to learn.
On the wrist
The case is just over 45 mm across and under 12 mm thick, which Casio sells as slim by G-Shock standards. It is light and flat enough to slide under a cuff more easily than most of its siblings, though the width means it still looks large on a small wrist. The resin strap is comfortable and has a standard keeper arrangement. The all-black finish goes with almost anything casual.
Water and everyday wear
It has a 200 m rating and is built for shocks and daily knocks. A carbon core guard structure gives the case rigidity. The crystal is mineral, and a raised bezel helps protect it. The LED light gives enough illumination to read the dial, and hands carry some lume for low light. It is a very practical watch that can handle swimming, cycling and the gym.
Against the alternatives
The Casio G-Shock GA-B2100-1AER adds Tough Solar and Bluetooth for a step up in convenience. The Casio G-Shock GA-2100TLS-8AER and Casio G-Shock GA-2100SKE-7AE give the same shape in different colours. If you prefer a square case, the Casio G-Shock DW-5600E-1V is the basic alternative. For a steel dress-sports look in the same spirit, the Tissot PRX T137.410.11.041.00 is a different kind of watch altogether.
Who it's for, and who should skip it
It suits people who want a modern, tough watch with a design edge, especially those who find traditional G-Shocks too chunky. Skip it if you want never to change a battery, since the solar version is better there, or if you want a dressy watch. Anyone with a very small wrist may find the case too large.
A researched review, built from the maker's specs, manual and Amazon.co.uk listing; facts checked 6 Nov 2026.
Who shouldn't buy this
Don't buy it if you want a watch that never needs a battery.
Key specs
| Movement | quartz |
| Calibre | Casio 5611 |
| Case | 45.4 mm |
| Thickness | 11.8 mm |
| Lug width | — |
| Water resistance | 200 m |
| Crystal | mineral |
| Strap | resin |
| Power reserve | — |
| Accuracy | ±15 s/month |
This is a Researched review: we haven't used this product. We check the maker's details against at least two independent sources, re-check the price where we can track it automatically, and say plainly who it isn't for. Commissions never change a rating.
If this isn’t the one
as of 6 Nov 2026, 13:25 GMT · Details
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.co.uk at the time of purchase will apply to the purchase of this product.
as of 6 Nov 2026, 13:25 GMT · Details
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.co.uk at the time of purchase will apply to the purchase of this product.