Gravitymaster GR-B300-1A4ER Watch

The Watch

Founded by Tadao Kashio in Mitaka, Casio has built a legacy of exceptionally rugged timepieces. Each model is crafted with precision by skilled watchmakers to deliver total accuracy, using robust materials and reliable mechanisms built to last. Today, the Japanese brand presents the Gravitymaster GR-B300-1A4ER Watch, inspired by next-generation aircraft. Designed for all genders, it features a round case crafted from bio-based resin reinforced with carbon fiber, ensuring rigidity and corrosion resistance. Finished in black, the case measures 54.70 mm wide, 59 mm long, and 15.70 mm thick, weighing 71 g. It is fitted with a gray bezel featuring a minute scale and marked with "G-Shock" and "protection" inscriptions. The bezel surrounds a mineral crystal that protects the dial and its various indicators. These are operated via 4 push-buttons and a screw-down crown positioned on the sides of the case. The crown features a screw-lock mechanism and is slightly knurled for easy grip. Finally, this watch offers water resistance to 20 ATM, ensured by its engraved screw-back case.

The Dial

This dial delivers clear, accurate readings every day. It features a gray base enhanced by a sandblasted finish for a refined satin effect. A LED illuminates it for approximately 1.5 seconds in the dark. The dial showcases a rehaut traced with a minute track and gray/orange hour markers. Three central hands sweep over the dial: a slim orange seconds hand, a long minutes hand, and a short hours hand. All hands feature a Neobrite coating for enhanced legibility when needed. A date window sits at 4 o'clock, alongside sub-dials at 4, 6, 9, and 12 o'clock for various functions. The small sub-dial features a small orange hand indicating A or P to denote AM or PM. The second sub-dial shows a second time zone in 12-hour format. The third indicates battery level, while the last displays the day of the week, alarm (AL), timer mode (TR), and chronograph mode (ST). Via the seconds hand, the dial also signals Bluetooth connection (C) or connection standby (R), AM (A) or PM (P), and alarm on (ON) or alarm off (OFF). Finally, the brand places its name at 3 o'clock along with the movement type and collection name as its signature.

Features

Time setting

Bluetooth: connects to a smartphone and automatically sets the time

Battery Power & Autonomy

Tough Solar (solar-powered)

Smartphone Link feature

Mobile Link (wireless connection via Bluetooth®)

Apps

CASIO Watches

App connectivity feature

Automatic time setting

Easy watch setting

300 cities for world time

Flight log

Phone finder

World time

Second time zone (home city time adjustment)

Chronograph

1-second stopwatch

Measuring capacity: 23:59'59.

Measuring modes: elapsed time, split time

Timer

Countdown timer

Measurement unit: 1 second

Countdown range: 24 hours

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

Alarm/time signal

Daily alarm

Illumination

LED illumination (Super Illuminator)

Afterglow

Light color

LED: white

Calendar

Full auto-calendar (until 2099)

Power saving function

Power saving (hands stop to conserve energy when the watch is left in the dark)

Battery level display/alert

Battery level indicator

The Movement

At the heart of this model is a solar movement. Robust and precise, it ensures the reliability of all functions. An integrated solar panel built into the display recharges the battery using natural or artificial light. Of Japanese origin, this movement is equipped with a cell providing a power reserve of approximately 5 months without light exposure, with an accuracy of ±15 seconds per month (without the Mobile Link function).

The Strap

This strap ensures all-day comfort in any situation. Durable and flexible, it is crafted from bio-based resin, making it perfect for any activity. Finished in black, it pairs effortlessly with all your accessories. It fits wrist sizes from 145 to 215 mm and features a double-lock pin buckle for easy adjustment.

Water Resistance

This model offers water resistance to 20 atmospheres, equivalent to 200 meters. This watch is built to keep up with your deepest aquatic adventures - including freediving! It handles high-pressure water jets with ease, so wear it confidently whether you're in the shower, the pool, or the open water. Shower, bath, lap swimming, and freediving are all fair game. That said, if you're planning a scuba dive with tanks, we recommend a timepiece with a higher water resistance rating. Also, avoid operating the crown or push-buttons while submerged to protect the mechanism's integrity.