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[G-SHOCK Blueooth] GA-B2100C-9A — Improved Oak with Bluetooth and Solar

I bought the latest model “GA-B2100” (GA-B2100C-9AJF) of G-SHOCK. It is a “BT solar” model that is not a radio wave solar but a solar power generation and Bluetooth compatible version of the recent hit model “GA-2100” series. The price was 18,480 yen at

The base GA-2100 was introduced in 2019 as a completely new work. It is a model that embodies the new generation of G-SHOCK by adopting a relatively simple design, a thin case, and a carbon core guard structure that realizes it. However, due to the low price range, the functions were simple and battery-powered. The GA-B2100 is equipped with the long-awaited solar power generation function and Bluetooth linkage function for this popular model. “B” is added to the model number to indicate Bluetooth compatibility. Here, we will mainly introduce the evolutionary points that have been added as “BT Solar”.

When a simple model is upgraded, it is often equipped with a time adjustment function by GPS or radio wave reception, but this model adjusts the time by periodically linking with a smartphone via Bluetooth. Casio officials say that it does not support the time-corrected radio wave reception function, because it is important that the module (movement) developed for this model is thin, so it was difficult to arrange the radio wave reception antenna. That is (although there may be other reasons).

Inevitably, I think that it will be a model that can be used as conveniently as possible when used in combination with a smartphone for people who use smartphones and Bluetooth functions on a daily basis.

Although it is the time adjustment function, the smartphone application “CASIO WATCHES” is used. The basic operation is that the app will be in the connection standby state in the background and will be connected only when there is a connection request from the clock. “Automatic time adjustment” is 6:30 am and 12:30 pm, four times a day. At this timing, the watch automatically connects to the smartphone via Bluetooth and the time is adjusted. Even in the sense of saving the battery on the watch side, it will not be connected automatically otherwise. You can also check the history of whether automatic time adjustment has been performed in the app.

Due to solar power generation and the installation of a battery, the display content of the hand at 9 o’clock on the dial has been changed. The GA-2100 used to indicate seven types of days from Sunday to Saturday, but the GA-B2100 indicates the current mode. Specifically, in addition to world time, stopwatch, timer, and alarm, the Bluetooth connection mode and the remaining battery level are shown in three types: High, Middle, and Low. In normal clock mode, the hands indicate the battery level.

The dial has a sunray finish with a radial hairline treatment from the center, which is not so noticeable, but the degree of reflection changes depending on the angle, giving it a slightly different atmosphere from the base model GA-2100.

The octagonal bezel, which is also a feature of the 2100 series, has no flashy irregularities on the surface and is a quiet design even in G-SHOCK. This is also a design realized because the concept of impact resistance has evolved by adopting a “carbon core guard structure”. In the past, the unevenness of the exterior was also part of the impact resistant structure, but since the carbon core guard structure is completed by the internal module, the exterior can be designed relatively freely.

The main body size is 48.5 x 45.4 x 11.9 mm (length x width x thickness). It weighs 52g. Compared to GA-2100, it is only 0.1mm thicker and weighs 1g, but I think the usability is almost the same.

The thickness is less than 12 mm, which is thinner than the 5600 series, which is based on the first model and can be said to be small now. It is thick enough to slip into the gaps in the sleeves of clothes such as shirts and trainers. The largest G-SHOCK model I own (GW-9400) has a width of 53.5 mm and a thickness of 18.2 mm, so it can hardly be stored in the sleeves of shirts and trainers, so GA- The B2100 seems to be a model that is easier to use on a daily basis.

GA-B2100 Profile / Casio G-Shock
Average Amazon Price: $180 (yes, we may earn a commission on qualifying purchases from our links to Amazon). Check the Price on Amazon →
Year of first release: 2022
The most distinctive specs:
— Retro Look (inherits the design concept of the very first G-SHOCK)
— Carbon Core Guard structure (protects the module by enclosing it in a carbon case. The case is made of fine resin embedded with carbon fibers for outstanding strength and crack resistance)
— Solar-powered (CASIO’s original solar-charging system converts not only sunlight but also light from fluorescent lamps and other sources into power)
— CASIO WATCH App (you may manage all watch settings through your phone)
— Mobile link (Wireless linking using Bluetooth(R)) (for time sync with your phone data)
— 200-meter water resistance (good for swimming but not for deep diving)
Other colors and full specs: GA-B2100 Wiki Page

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