Casio G-Shock Master of G-Air Gravitymaster - GRB300-1A4

The sky’s the limit! Introducing the GRAVITYMASTER GRB300,
a piece of aviation-inspired professional gear designed to work
even in the harshest environments, from the G-SHOCK MASTER
of G line.

The GRB300 features a Carbon Core Guard structure, which delivers 
the shock-resistance, rigidity, and corrosion-resistance of carbon 
material used in aircraft fuselages. The carbon fiber-reinforced 
resin case & the seamless bezel design inspired by next-generation 
aircraft come together in a bold and powerful form. 

Envision the world through a pilot’s eyes with the flight log memory 
function for recording current location and time, as well as dual-time 
simultaneously displaying the time in two time zones. In addition, 
simply tap on the app to instantly switch between the time back home 
and local time — a practical function to make traveling abroad that 
much smoother.

Large, dimensional index marks and a metal bezel accentuating
the large watch face exude functionality, enhancing the visibility
that is so important for pilots, whose job demands intuitive reading
of time.

The rotary disc indicator at the 9 o’clock position uses a dual-coil 
motor to ensure smooth rotation and functional beauty. 
The indicator not only rotates to display alarm on/off and stopwatch; 
it functions as a battery level indicator as well.

The high-contrast black and white color scheme dotted with color accents 
on the dial and buttons evokes the look of a cockpit instrument panel, 
while dark color variations express the practical functionality of 
an aviation worldview.

Key resin components used in the case, bezel, and band are made with 
bio-based resin, a material expected to help reduce environmental impact.

Case size: 59 × 54.7 × 15.7 mm
Weight: 71 g
Case & bezel material: Carbon / Bio-based resin
Band: Bio-based resin band
Construction: Shock Resistant
Carbon Core Guard structure
Water resistance: 200 meters
Time adjustment
Bluetooth: Connects to a smartphone & automatically adjusts the time
Power supply and battery life: Tough Solar / Solar powered

Smartphone Link/App Connectivity Features 
Smartphone Link feature: Mobile link (Wireless linking using Bluetooth®)

Apps
CASIO WATCHES

App connectivity feature
Auto time adjustment
Easy watch setting
Approximately 300 world time cities
Phone finder

Exterior
Glass: Mineral Glass
Crown: Screw Lock Crown
Compatible band size: 145 to 215 mm
Other: Neobrite

Watch Features

World time
Dual time (Home City time swapping)

Stopwatch
1-second stopwatch
Measuring capacity: 23:59'59.
Measuring modes: Elapsed time, split time

Timer
Countdown timer
Measuring unit: 1 second
Countdown range: 24 hours
Countdown start time setting range: 1 minute to 24 hours 
(1-minute increments and 1-hour increments)

Alarm/hourly time signal
Daily alarm

Light
LED light (Super Illuminator)
Afterglow

Light color
LED:White

Calendar
Full auto-calendar (to year 2099)

Energy saving feature
Power Saving (hands stop to save power when the watch 
is left in the dark)

Battery display / alert
Battery level indicator

Run time
Approx. battery operating time:
5 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)

Accuracy
Accuracy: ±15 seconds per month (with no mobile link function)

Other features
Date display
Day indicator
Regular timekeeping:
Analog: 3 hands (hour, minute (hand moves every 10 seconds), second), 
3 dials (dual time hour and minute, dual time 24-hour, day)