Casio G-Shock Men's 54mm GRB100-1A3 Resin Watch - Black/Green

Constantly setting new standards for timekeeping, G-Shock is synonymous for providing the best of both analog and digital formats in a lightweight, styling package suited for the outdoor explorer or weekday warrior. The GRB100-1A3 is no exception. Featuring a double LED light, solar powered operation, world time across 39 cities, 5 multi-function daily alarms, 1/1000-second stopwatch, countdown timer, and a full-auto calendar ensuring you never miss an appointment. And as always the classic G-Shock protection, a combined resin and stainless steel case, a huge 200 metre water resistance and mobile link technology for even more control from your phone.


  • Casio G-Shock watches
  • Model: Gravitymaster
  • Model no.: GRB100-1A3
  • For men
  • Movement: Quartz
  • Dial colour: Grey
  • Band colour: Black/Grey
  • Case colour: Black
  • Case material: Resin/stainless steel backing
  • Band material: Resin
  • Band measurement (approx. mm):
    • Width: 20
    • Length including the face: 250
  • Case diameter (approx. mm, includes casing): 54
  • Case thickness (approx. mm): 17
  • Clasp type: Buckle
  • Water resistance: 200m (20ATM)
  • Shock and magnetic resistant
  • Mineral glass
  • Mobile link (Wireless linking using Bluetooth)
  • Double LED light
    • LED light for the face (Full auto LED light, Super illuminator, selectable illumination duration (1.5 seconds or 3 seconds), afterglow)
    • LED backlight for the digital display (Full auto LED light, Super illuminator, selectable illumination duration (1.5 seconds or 3 seconds), afterglow)
  • World time:
    • 39 time zones (39 cities + coordinated universal time)
    • One-touch UTC time zone
    • Daylight saving on/off
    • Auto summer time (DST) switching
    • Home city/World time city swapping
  • Stopwatch:
    • Measuring capacity:
      • 00'00"000~59'59"999 (for the first 60 minutes)
      • 1:00'00"0~23:59'59"9 (after 60 minutes)
    • Measuring unit:
      • 1/1000 second (for the first 60 minutes)
      • 1/10 second (after 60 minutes)
    • Measuring modes: 
      • Elapsed time
      • Split time
  • Countdown timer
    • Measuring unit: 1/10 second
    • Countdown range: 24 hours
    • Countdown start time setting range: 1 second to 24 hours (1-second increments and 1-hour increments)
  • 5 multi-function alarms (with countdown, daily, 1 time, schedule)
  • 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 and hands stop to save power when the watch is left in the dark)
  • Regular timekeeping:
    • Analog: 3 hands (hour, minute), 1 dial (countdown indicator)
    • Digital: Hour, minute, second, pm, month, date, day
  • Accuracy: ±15 seconds per month
  • Battery: Solar
  • Battery life: 6 months (without exposure to light); 19 months (in total darkness w/ power save function on)
  • Original box: Yes - ready for gift giving!
A Bit About The Brand / More Info

Casio has been crafting timeless designs for decades. Renowned for their combination of flair and versatility, Casio wrist watches are perfect for anyone who requires unique functionality to go.

Product Reviews


5 Star
4 Star
3 Star
2 Star
1 Star

30 August 2019

Great watch. Works and looks great and solar function does work as mine has charged from wearing it in the sun.

1 customer found this helpful

Was this helpful? YesNo

05 June 2019

Great watch, highly recommended

Was this helpful? YesNo

18 June 2020

Great item

Was this helpful? YesNo

17 July 2020

11 June 2020