Casio G-SHOCK GM-B2100BD-1AER:


Let's face it, Casio's latest G-SHOCK, the GM-B2100, is one of the most anticipated watches of the year. And also one of the most high-end of G-SHOCK. It has everything to please: an octagonal bezel in reference to one of the most emblematic watches in the sector, a steel case and bracelet (a first for G-SHOCK!), functions connected via Bluetooth, and a possibility of recharging it in the sun (and in artificial light) which ensures an almost unlimited autonomy. We were able to test the GM-B2100BD-1AER, the version with a black steel case and bracelet, for almost 3 weeks. Verdict of Mr Watch!




A Casioak in reference to the Royal Oak


As a reminder if the name GM-2100 only vaguely reminds you of something, this is a range of watches nicknamed "CasiOak" (or "Casioak") because of the octagonal shape of its bezel. reminiscent of the iconic Royal Oak by Audemars Piguet.


Sober and aesthetic, easy to use, hardened, and affordable, this range of watches has met with great success since its release. Based on this winning recipe, the brand has therefore decided to decline the Casioak this year , and has been offering us a “full metal” version called GM-B2100 for a few days . This model of the 2100 series is inspired by the DW-5000C, the first G-SHOCK launched in 1983 by Casio.



Casio G-SHOCK GM-B2100BD-1AER watch review


This new G-SHOCK more precisely takes up the codes of the all-metal watches initiated in 2018 by Casio. There are three distinct models this year:


GM-B2100D-1AER with a classic steel case and bracelet (€549)

GM-B2100BD-1AER with a black steel case and bracelet, the version tested on MrMontre (€599)

GM-B2100GD-5AER still in steel but with copper shades (€599)

All these G-SHOCK of the GM-B2100 range have a slightly larger case than that of the resin G-SHOCK GA-2100 models: 49.8 mm × 44.4 mm for 11.9 mm thick. And it's also the thinnest metal G-SHOCK ever made.


We have set our sights on the “full black” GM-B2100BD-1AER model, which is our favorite version. Will it stand out from similar resin models, like its counterpart GA-2100-1A1ER billed “only” €99 (or even the GA-B2100-1A1ER at €149)? This is obviously the question we also asked ourselves!


First look: Design tool watch, multifunction dial characteristic of G-SHOCK, octagonal bezel, analog hour/minute hands, seconds and additional functions via a digital screen, curved link bracelet (48.5 mm case).



The box

The use of metal on a G-SHOCK watch is nothing new! Already in the summer of 2021, Casio was offering the GM-2100 for around €200 , a “Casioak” equipped with an octagonal metal bezel, the strap remaining in resin. This year, with the GM-B2100 series, a 100% steel model (bracelet + bezel + case) is therefore offered.


The steel case has a diameter of 48.5 mm and adapts to the majority of wrists, the watch is thin (only 11.9 mm thick ) and the caseback is solid and screwed down. The octagonal bezel has been polished in a circular fashion which gives it a very pleasant shine.


The dial is protected by a mineral  glass – we would have clearly preferred a sapphire crystal -, for a general look that stands out from other G-SHOCK models designed mainly for adventurers.


Here, the GM-B2100 certainly has a "  shockproof structure ", as Casio specifies on its website, but it is clear that with its mineral glass less resistant than a sapphire crystal, and above all a price which is around 600 €, we cannot keep it on our wrist when moving house or in the middle of a rugby match. We risk damaging it!


Yet Casio wants to be reassuring by adding that “ fine resin damping elements are placed between the stainless steel bezel and the case to protect the module from shocks. The bezel and case are precision assembled in a meticulous forging, cutting and polishing process, which also extends to the front and back of the case, ensuring a high level of precision. and adjustment.


In addition, the case has a structure with three ribs to distribute the shocks on the connecting part of the bracelet”. In any case, we could perfectly wear it with a formal outfit ! A "classic" G-SHOCK, in resin, would not have had the same luck.


It should also be noted that this tool watch is equipped with four push-buttons at the four corners of the case (2 o'clock, 4 o'clock, 8 o'clock and 10 o'clock) making it possible to illuminate part of the dial via a white LED located between 4 o'clock and 5 o'clock, to change mode or to interact with its functions, connected or not connected.


The buttons are not screwed but this still allows it to be waterproof to 200 meters . You can therefore keep it on your wrist in the shower or at the sea without any problem!



The dial & reading the time


(The day dial / The night dial illuminated by the white LED)


The dial of this GM-B2100BD-1AER is recognizable among a thousand! You just need to have already had (or seen) another G-SHOCK to understand how to use its dial. For the others, it's not very complicated even if it still requires a little time to adapt .


First of all, there is a reading of the time in analog form using two hour / minute hands (at the luminescent tip) which turn around 12 matte black stick indexes (at the luminescent end as well) and a railway of minutes .


There is also the possibility of reading the time in digital form thanks to the 2-line LED screen which can be used to display the date of the day, to access the parameters of the watch or all of its additional functions. .


Finally, there is a circular sub-dial from 8 to 10 o'clock which allows you to activate/configure the Bluetooth link, to consult the charge level of the watch (L for Low, M for Medium and H for High) or to access to its different modes in one click:


WT for World Time

ST for stopwatch

TR for timer mode

AL for alarm

The four push-buttons located on the corners of this G-SHOCK all have a very specific use : switch from one mode to another (MODE button), adjust the parameters of the mode in question (ADJUST button), turn on the LED white to illuminate the screen (LIGHT button, the LED lighting time can also be configured) and launch an action (START button).


For the rest, we find on the dial of this GM-B2100BD-1AERthe mention "G-SHOCK" in addition to the discreet "CASIO" at 12 o'clock.




Bluetooth mode and connected functions


The G-SHOCK GM-B2100 incorporates a function called Mobile Link which has made the success of other rugged Casio watch models: a Bluetooth connection allows the watch to be linked to the smartphone via an application compatible with Android / iOS smartphones to add connected functions. Please note that the application in question is called Casio Watches and not G-SHOCK “just short” or G-SHOCK Connected.


The connection between the watch and the smartphone is child 's play : you switch to Bluetooth mode, launch the app and let yourself be guided. From the first synchronization, the time is automatically set on the watch! Practice !


What about the connected functions of this watch? We tested them all:


Automatic time adjustment : just link the smartphone to the watch. Time synchronization is done 4 times a day

Easy setting of the watch : it is possible to modify all – or almost – the parameters of the watch: duration of illumination of the watch, switching to energy saving mode, alarms, timers, setting of sounds, duration of connecting with the app...

300 cities for world time : you have to choose one, displayed automatically by activating the "WT" mode for World Time

Manual adjustment of the hands : for maniacs who want the hands to be very precisely at 12 o'clock (and not shifted by a few millimeters)

Reminder : so that the watch reminds us, for example, of an appointment or an anniversary date. It is possible to display the title of this reminder on the watch screen. Events must be filled in manually. You cannot sync your smartphone calendar or Google Calendar.

Phone Locator Tool : Lost your phone? Just click a button on the watch to ring the phone. The ringtone – and the volume – are configurable

Interesting detail, the application on the smartphone also provides access to the user manual of the watch, and tutorials to better use it.



The G-SHOCK GM-B2100BD-1AER is powered by an in-house movement, but Casio does not specify whether it is a quartz movement. Anyway, it is a rechargeable battery which is inside the watch and which allows you to benefit from a double analog display via hour / minute hands, and digital via a multifunction LCD screen.


The use of this technology allows it to have an accuracy of ±15 seconds per month . And even much higher if the watch is connected via Bluetooth to the smartphone. The watch can then automatically connect to the phone four times a day to set its time. It is of course possible to deactivate this function in a few seconds to preserve your battery or that of your smartphone.


On the autonomy side , note that the GM-B2100 incorporates a “Tough Solar” solar function (mentioned on the dial of the watch at 3 o'clock) offering easy recharging through light (natural or artificial). Its power reserve is announced at 7 months in normal use and without exposure to sunlight, or up to 18 months with the energy saving function activated.


To recharge it for one day of use , it only takes 8 minutes in direct sunlight or 8 hours with artificial light from a desk. For information, we therefore wore our test GM-B2100BD-1AER for more than 3 weeks and its autonomy displayed via a complication located at 9 o'clock has not changed one iota. However, we are coming to the end of summer and we haven't been out in the sun for long!




The bracelet



There's a lot to be said for the stainless steel bracelet that equips our GM-B2100BD-1AER . First of all, it is very comfortable to wear thanks, among other things, to its thinness, its manufacturing quality and its first link which on either side of the case is curved to fit the shape of the wrist.


It is also easily adjustable to the size of his wrist. There is no need to use a pump puller or similar tool to remove links. We used the same sharp tool as for accessing a smartphone's SIM card (or a simple paper clip!) to remove the superfluous links one-by-one.


Thanks to its many vents between each link , it is one of the rare bracelets that can be worn in summer, without discomfort, and which is still comfortable for small and large wrists. Four micro-adjustments on the clasp are offered (you have to use the same tool / paper clip to access them) to more or less tighten the bracelet in summer or winter.


The clasp is moreover rather well designed, with triple folding clasp with simple pressure . The clasp would probably have deserved to be a little stronger in use in our opinion. Finally, note that the bracelet, which uses the curved links of the metal bracelet of the DW-5000C, alternates between brushed and polished elements, which does not spoil anything!


Technical recap

Case: stainless steel

Size: 48.5mm

Thickness: 11.9mm

Weight: 165 grams

Dial: 3D, analog display (hour/minute hands) and digital one via LCD screen, indexes and hands equipped with NeoBrite + Super Illuminator LED for better readability at night

Movement: guaranteed accuracy of ±15 seconds per month without connection to the smartphone, 7-month power reserve if not worn, solar charging function

Glass: mineral

Case back: screwed, solid

Strap: steel, triple folding clasp with single pressure

Water resistance: 20 ATM / 200m

2 years warranty




Mr Montre's opinion on the Casio G-SHOCK GM-B2100BD-1AER


As you will have understood from reading this (long) test, we fell in love with this G-SHOCK GM-B2100BD-1AER. At first we were a little scared, given its technical characteristics, its size – with a rather imposing diameter of 48.5 mm -, and its weight – with 165 grams on the scale -.


But it is clear that even on our small wrist, this G-SHOCK is not oversized . And once the strap was adjusted – with a watch that now weighs around 150 grams once the superfluous links have been removed – it was quickly forgotten. Without (any) discomfort.


After putting it on the wrist for more than three weeks, we gradually discovered some of its hidden functions . Because this GM-B2100BD-1AER is an (almost) connected watch that is quite atypical and above all very practical . Synchronizing the time with the smartphone is very useful, as is the function to reverse local time and GMT time (practical for frequent travellers).


The other functions offered are numerous: ring the smartphone to find it, for example, hide the hands by pressing the "light" (2s) + mode buttons and thus read the information from the LCD screen, read the time in analog form or digital, the luminescent indexes AND the white LED which illuminates the dial, the reminder of dates/events thanks to the associated smartphone app...


As long as you take, like us, the time to read the user manual , you will appreciate this watch all the more. For the most curious, it is obviously not a smartwatch: it does not have a GPS chip, does not read smartphone notifications and does not allow you to count steps or pick up / hang up. But all its functions, in addition to its LCD screen, have no impact on its autonomy: thanks to the solar charging function ! With 7 months of power reserve, and the possibility of charging it for an extra day's use in just a few minutes in direct sunlight, it is difficult to do better !


Not everything is perfect, however, such as the mineral crystal which could (should?) have been a sapphire crystal – more resistant and less sensitive to scratches -, or the bracelet clasp which could have been more secure, but we have to to see that this first 100% metal G-SHOCK is a success ! Which certainly pays a high price, €599 for our 100% black steel model, but which in our opinion should be considered a tool watch , or even a dress watch in certain situations, rather than a "simple" watch for sportsmen and women. /or adventurers.



-> Buy the Casio G-SHOCK GM-B2100BD-1AER