The Casio G-Shock Gravitymaster GR-B300 pairs a large, aviation-inspired analog display with dual-city time, Tough Solar charging, Bluetooth phone features and 200-meter water resistance. It is a substantial watch by its published dimensions, and its flight log relies on a paired smartphone rather than independent onboard GPS. Casio lists GR-B300-1A, GR-B300-1A4 and GR-B300-8A2 on its US product page; exact colors, stock and prices depend on market.
What the GR-B300 is—and what it is not
The GR-B300 is part of Casio’s G-SHOCK MASTER OF G AIR GRAVITYMASTER line. Casio positions it around aviation and cockpit-instrument design, with a metal bezel, layered three-dimensional dial, raised indices and a seamless-looking case-to-band profile. That is design intent, not evidence that the watch is aviation-certified or suitable as a flight-critical instrument. Casio’s product descriptions establish features and specifications, not independent aviation performance.
Casio’s US page names three references: GR-B300-1A, GR-B300-1A4 and GR-B300-8A2. The reference list does not establish current availability in every country, so check the suffix and local stock before buying.
Is the GR-B300 too large?
Casio India lists the GR-B300-1A4 at 59 × 54.7 × 15.7 mm and 71 g. Those dimensions make it a large, thick watch on paper; whether it suits a particular wrist depends on fit and preference. The figures are for that India-market reference, not a universal fit assessment.
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- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
Casio says the GR-B300 case is about 4 mm shorter from 12 to 6 o’clock and 2.8 mm thinner than the preceding GR-B200. This is a manufacturer-reported comparison, not an independent measurement. The India specification also lists mineral glass, a carbon/bio-based resin case and bezel, and a bio-based resin band. “Bio-based” describes material sourcing; the cited material does not quantify a lifecycle or environmental benefit.
Display, timekeeping and daily functions
The GR-B300 is fully analog: its main and inset dials show the time in two cities simultaneously. Casio says the CASIO WATCHES app can configure world time and switch between home time and world time. This arrangement favors a quick view of two time zones without navigating a digital display, while the broad case and layered dial are part of its aviation-inspired styling.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
- Time and calendar: dual time, date and day display.
- Timing: stopwatch and countdown timer.
- Alerts: alarm.
- Lighting: Super Illuminator LED.
- Power and connection: Tough Solar charging and Bluetooth smartphone link.
- Protection: shock resistance and 200-meter water resistance.
Casio’s US feature list says automatic time adjustment occurs four times a day and lists world time for about 300 cities. These are the manufacturer’s stated app features; actual setup and availability depend on the phone app and market.
What does the flight log actually record?
Casio describes a phone-assisted flight log, not an independent GPS tracker built into the watch. After synchronizing the watch with a smartphone, the wearer presses a watch button to save the current time and position to a map in the app. Casio says mapped points can be grouped as travel or flight records. The description does not establish continuous route tracking or onboard GPS positioning.
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Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Casio’s US product page warns: “This app is currently in development, and specifications are not yet final.” Treat the flight-log workflow as a promised app feature whose details may change, rather than a guaranteed substitute for a dedicated navigation or flight instrument.
Construction and the GR-B200 connection
Casio says its Carbon Core Guard structure uses carbon-fiber-reinforced resin to protect the movement, combining strength with lightness. The GR-B300’s layered bezel uses metal and urethane rings; Casio describes the case as carbon-fiber-reinforced resin. The watch also uses bio-based resin in key components, without a quantified environmental claim in the cited specifications.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
The GR-B300 follows the GR-B200, which Casio says was released in August 2020. In Casio’s account of development, the updated structure brings a metal bezel into engagement with the reverse side of a resin guard. The brand says it interviewed professional pilots while revisiting the design, returned to a fully analog presentation, and replaced the earlier digital window with a dual-time display. These are Casio-reported design choices and aims, not independent findings that the watch performs better in a cockpit.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Price, references and what to check before buying
Casio India lists the GR-B300-1A4 at ₹22,995 including taxes as its market-specific MRP. That is not a global price or a guarantee of current street pricing. The reviewed manufacturer pages do not establish a comparable current US or European price.
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Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
- Match the exact suffix and color to the listing; the documented US lineup includes GR-B300-1A, GR-B300-1A4 and GR-B300-8A2.
- Check the official local Casio page for regional price and availability, then verify the seller’s identity and return terms.
- Consider the published 59 × 54.7 × 15.7 mm dimensions for the GR-B300-1A4 if case size is a concern.
- If the flight log matters to you, check the current CASIO WATCHES app description and compatibility information before purchase.
- Do not assume a replacement band is compatible based on appearance alone; the cited pages do not verify a replacement-band part number or third-party fit.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
