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Casio G-Shock GRB300-8A2 GRAVITYMASTER Bluetooth Solar Gray Blue Accents Watch


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  • 30 day returns
  • Free shipping
  • Secure checkout
  • 6-month warranty

At a Glance

The sky’s the limit! Introducing the GRAVITYMASTER GR-B300, a piece of aviation-inspired professional gear designed to work even in the harshest environments, from the G-SHOCK MASTER of G line.

The GR-B300 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 and 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.

An organic form inspired by next-generation aircraft is expressed.


  • Aviation Inspired
  • Bluetooth Connectivity
  • Carbon Core Guard Structure
  • Tough Solar Powered
  • Shock Resistant

Included with Purchase

  • Casio G-Shock GRB300-8A2
  • G-Shock Outer Box
  • G-Shock Inner Tin
  • Instruction Module
  • 1 Year Casio International Warranty Card

Watch Features

World Time

  • Dual time (Home City time swapping)


  • 1-second stopwatch
  • Measuring capacity: 23:59’59.
  • Measuring modes: Elapsed time, split time


  • 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


  • 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: ±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)

Smartphone Link – App Connectivity Features

Smartphone Link feature

  • Mobile link (Wireless linking using Bluetooth®)



App connectivity feature

  • Auto time adjustment
  • Easy watch setting
  • Approximately 300 world time cities
  • Flight log
  • Phone finder


  • Glass – Mineral Glass
  • Crown – Screw Lock Crown
  • Compatible Band Size – 145 to 215mm
  • Other – Neobrite

Basic Information

Time adjustment

  • Bluetooth: Connects to a smartphone and automatically adjusts the time

Tough Solar (Solar powered)


  • Shock Resistant
  • Carbon Core Guard structure

Case and bezel material

  • Carbon / Bio-based resin


  • Bio-based resin band

Water resistance

  • 200-meter water resistance

Case size (L× W× H) – 59 × 54.7 × 15.7 mm
Weight – 71g

Shock Resistant

Stable solar power

Keeps yourself in time

20 bar water resistant

Shock Resistant

Reviews & Ratings

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