An ultra-thin module encased in carbon fiber makes for a stylish G-STEEL timepiece with the slimmest profile yet.

Strong, yet lightweight, the carbon core guard structure absorbs external shocks and retains Bluetooth connectivity and solar power functionality even with smaller components and a thinner module. Measuring just 12.9mm from the back of the case to the top of the bezel, the GST-B400 is over a millimeter thinner than its predecessor .

Your choice of four distinctive styles the simplicity of a silver metal band and silver case; light silver case set against dark resin band; dial in dramatic red vapor deposition finish paired with a black ion-plated bezel; or dial in bold blue vapor deposition finish with black ion-plated bezel and band. With top bezels treated with five different finishes and middle bezels treated with four, these G-STEEL timepieces deliver exceptional metal textures from every angle.

* Slimmest profile as of December 2020

• Case/bezel material: Resin / Stainless steel
• Solid Band
• Stainless Steel Band
• One-touch 3-fold Clasp
• ShockÇ?ÇîÇ??Resistant
• Neobrite
• Mineral Glass
• Carbon Core Guard structure 
• 200-meter water resistance
• Tough Solar (Solar powered)
• Double LED light
• LED light for the face (Super illuminator, selectable illumination duration (1.5 seconds or 3 seconds), afterglow)
• LED backlight for the digital display (Super illuminator, selectable illumination duration (1.5 seconds or 3 seconds), afterglow)
• LED: White
• Mobile link (Wireless linking using Bluetooth) 
• World time
• 38 time zones (38 cities + coordinated universal time), city code display, city name display, daylight saving on/off, auto summer time (DST) switching, Home city/World time city swapping
• 1/100-second stopwatch
• Measuring capacity:
• 00'00''00~59'59''99 (for the first 60 minutes)
• 1:00'00~23:59'59 (after 60 minutes)
• Measuring unit:
• 1/100 second (for the first 60 minutes)
• 1 second (after 60 minutes)
• Measuring modes: Elapsed time, lap/split time
• Countdown timer
• Measuring unit: 1 second
• Countdown range: 60 minutes
• Countdown start time setting range: 1 second to 60 minutes (1-second increments and 1-minute increments)
• 5 daily alarms
• Hourly time signal
• Hand shift feature (Hands move out of the way to provide an unobstructed view of digital display contents.)
• Battery level indicator 
• Full auto-calendar (to year 2099) 
• 12/24-hour format 
• Button operation tone on/off
• Power Saving (display goes blank to save power when the watch is left in the dark)
• Date/month display swapping
• Day display (days of the week selectable in six languages)
• Regular timekeeping:
• Analog: 2 hands (hour, minute (hand moves every 20 seconds)), 1 dial (battery level, mode)
• Digital: Hour, minute, second, pm, month, date, day
• Accuracy: +/-15 seconds per month (with no mobile link function)
• Approx. battery operating time:
• 7 months on rechargeable battery (operation period with normal use without exposure to light after charge)
• 18 months on rechargeable battery (operation period when stored in total darkness with the power save function on after full charge)
• Size of case: 46.6 x 49.6 x 12.9 mm
• Total weight: 160 g