G-Shock’s latest aviation-themed Gravitymaster is a Master of G, meaning it’s made for the harshest environments.
Casio launched the new Gravitymaster GRB300 collection in 2024 with three variations (GRB300-1A, GRB300-1A4, and GRB300-8A2). This review focuses on the GRB300-1A — which has a sporty, classic black, white, and red combination.
G-Shock says the Gravitymaster is “a piece of aviation-inspired professional gear” and accordingly the case takes cues from aircraft fuselages, the dial is designed for high visibility, there’s a chronograph that can display elapsed time, dual illumination is available for lowlight cockpit conditions (lume and LED), there’s a dual time display, and the electronic crown which allows for manual setting of the time — are all useful to a pilot.
The Gravitymaster GRB300 case measures 54.7 mm x 15.7 mm (48 mm without the crown guards) and 59 mm (lug-to-lug). Its sizable dimensions allow for a highly legible dial — excellent legibility is a prerequisite of any aviation-focused watch. Four large flat pushers allow the watch functions to be operated more easily than with smaller, recessed buttons. The 7.5 mm diameter electronic crown (non-locking) is large enough to be adjusted easily, and the crown guards do not interfere. Despite the dimensions, the Gravitymaster GRB300 weighs just 71 grams. I’d recommend it to people with medium to larger wrists, or those that love larger watches.
The case, bezel, and band are made with bio-based resin, a material expected to help reduce environmental impact. A Carbon Core Guard structure for the inner case delivers high shock resistance, rigidity, and corrosion resistance. The carbon fiber-reinforced resin case and the seamless bezel design were inspired by next-generation aircraft and have an aerodynamic aesthetic.
Casio gave the Gravitymaster Bluetooth functionality that allows the wristwatch to connect to your smartphone and automatically adjust the time for you. Additionally, once connected to the Smart Link via the Casio Watches App, you can use the flight log memory function to record the current location and time. The app also lets you control numerous other functions, including the dual-time function (with AM/PM indicator).
The rotary disc indicator at the 9 o’clock position uses a dual-coil motor to ensure smooth rotation. The indicator rotates when the top left button is pushed (which changes modes), indicating a change between AL (alarm), TR (countdown timer), and ST (stopwatch/chronograph) modes. It would be cool to see the disc rotating continuously, or every 20 seconds, but the battery life would likely suffer too much to make that a viable option.
The high-contrast display of the dial is meant to evoke the look of a cockpit. Large hands, large indices (and Arabic numerals at 12 and 6), make reading the time easy to do at a glance, a key design element of any pilot watch. Being a G-Shock there’s a lot of added functionality as well, and though the dial is clean, some of the fonts, such as on the left side of the 12’clock function indicator (right shows the day of the week). I wonder if the day of should have been omitted in favor of better optics for the function indicator. In my use case, I would have preferred that.
Traditional painted-on luminous material coats the hour and minute hands, as well as the ten indices. The 12 and 6 o’clock were not given a luminous treatment, though it would have certainly improved low-light visibility. That said, there’s also a white LED light that can be activated at the press of the button.
A stainless steel caseback, engraved with the “SHOCK RESIST” shield, the G-Master mark, and other relevant specifications, such as a 20ATM water resistance rating (200 meters), is secured to the caseback via 4 traditional screws that are slotted for a flat or Phillips head screwdriver.
To save power, the watch automatically stops the hands when left in the dark. Saving additional power, the minute hand only moves every 10 seconds. Total run time is approximately 5 months on the rechargeable battery (operation period with normal use without exposure to light after charge) and 18 months on the rechargeable battery (operation period when stored in total darkness with the power save function on after full charge).
Functionally, the Gravitymaster has a stopwatch (with 1-second accuracy, able to measure up to 24-hour periods, both elapsed and split times), a countdown timer (with a 1-second readout that can countdown from as high as 24 hours), an alarm that can be turned on and off, all selected with the mode button. Additionally, the Gravitymaster offers a dual time function (with an AM/PM indicator that can be easily controlled by the Casio Watches app), a date display and day indicator (that is accurate until the year 2099), and a phone finder.
Verdict
The Gravitymaster GRB300 collection features a quartz module that recharges automatically via solar power (both artificial and natural light), Bluetooth time automatic syncing once connected to the Casio Watches app, accurate to -15/+15 seconds per month even when not connected to Bluetooth.
Overall the dial is clear and highly legible, which is an absolute requirement of a pilot-focused watch. And there are not too many functions to the point that it gets overwhelming.
Casio has enhanced the look, functionality, and sustainability of its Gravitymaster — a dual-time, pilot-style watch, for the smartphone age.
The retail price is $300. Learn more at G-Shock.
SPECIFICATIONS:
Gravitymaster
Reference: GRB300-1A
Year: 2024
Total Weight: 71 grams
Case Material: carbon/bio-based resin/stainless steel
Case Diameter: 54.7 mm (48 mm not including crown guards)
Case Thickness: 15.7 mm
Lug-to-lug: 59 mm
Crown Diameter: 7.5 mm (non-locking, protected by crown guards)
Glass: mineral crystal (armored)
Movement: Japanese Quartz Module 5719
Depth Rating: 200 meters
Strap: 22 mm/20.5 mm
