Casio G-Shock GST-B400BB-1AER

About the watch

The monochromatic color scheme makes the GST-B400BB-1AER a more subdued interpretation of G-STEEL, but the front still has a dense, technical structure. Dark hands, digital fields, and raised markers work on multiple levels rather than through strong color contrasts. The result is a sports watch with a clear fashion character, where the ana-digi display and cohesive profile provide a controlled expression from dial to strap.

Materials & fit

The case measures 46.6 × 49.6 mm and is 12.9 mm thick. The weight is 80 grams. Resin and stainless steel are used in the case and bezel, with black ion plating over the metal parts. Mineral glass protects the combined display. The black strap is made of resin, and Casio states a compatible wrist circumference of 145–215 mm. The slim combination module keeps the profile lower than the wide front initially suggests.

Highlights

• The Carbon Core Guard structure and shock-resistant design are built for G-Shock's robust basic format.
• Tough Solar provides approximately seven months of operation without new light exposure or 18 months in darkness with power-saving mode.
• Bluetooth and the CASIO WATCHES app manage automatic time adjustment, settings, Time & Place, reminders, and phone finder.
• Water resistance to 20 ATM is specified for swimming and diving.

Good to know

• How extensive is the world time function? The watch handles 38 time zones, while the app provides access to about 300 world time cities.
• What can the stopwatch do? It measures hundredths of a second during the first hour and continues for up to 24 hours with lap and split times.
• How long is the timer? The countdown can be set between one second and 60 minutes.
• How is readability improved? White dual LED illuminates the dial and display, while Hand Shift moves the hands away from the digital information.
• What precision is stated without mobile connection? The deviation is ±15 seconds per month.