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The GG-B100-8AER Mudmaster and GR-B200-1B Gravitymaster are black-and-grey G-SHOCK Master of G models from 2021. They share core functions—including Bluetooth time adjustment, four sensor types, shock resistance and 200-metre water resistance—but differ in series identity, stated resistance, dimensions, weight and listed case materials. The Mudmaster is Casio’s land-oriented choice; the Gravitymaster is positioned for air and pilot use.
How the two 2021 models differ
| Specification | GG-B100-8A MUDMASTER | GR-B200-1B GRAVITYMASTER |
|---|---|---|
| Series and stated orientation | Land-oriented MUDMASTER; Casio describes the range for harsh terrain | Air-oriented GRAVITYMASTER; Casio positions it for pilots in harsh environments |
| Case dimensions | 55.4 × 51.3 × 19.4 mm | 63 × 54.1 × 18.3 mm |
| Weight | 92 g | 80 g |
| Case and bezel materials | Carbon/resin | Carbon |
| Additional stated resistance | Mud resistance | Vibration resistance |
| Shared construction and resistance | Carbon Core Guard structure, shock resistance and 200-metre water resistance | |
| Functions | Step count, altimeter, barometer, digital compass, thermometer and Bluetooth smartphone time adjustment | |
| Battery | CR2025; approximately two years’ battery life, according to Casio | |
These are Casio’s published specifications, not independent comparative test results. See the GG-B100-8A official product page and GR-B200-1B official product page for the listed details.
Which one fits your intended use?
Choose the GG-B100-8A MUDMASTER for the land-oriented series
Casio associates the MUDMASTER line with harsh terrain, including rubble, earth and sand, and the GG-B100-8A lists mud resistance. Its published dimensions are smaller in length and width than the Gravitymaster’s, though it is 1.1 mm thicker and weighs 12 g more. That makes its specification profile the more terrain-focused one, not proof that it will outperform the other model in a particular field condition.
Choose the GR-B200-1B GRAVITYMASTER for the air-oriented series
Casio positions the GRAVITYMASTER line for pilots in harsh environments, and this model lists vibration resistance. It is longer and wider than the Mudmaster but thinner and lighter. Those figures may help with a fit comparison, but they do not establish how either watch will feel on an individual wrist.
#1 Best Overall
- Featuring a Black Band, Black Case, Scratch Resistant Mineral Crystal
- International products have separate terms, are sold from abroad and may differ from local products, including fit, age ratings, and language of product, labeling or instructions
- Original box and packaging: Watch back, but it might be different in the printed image
- Scratch resistant mineral
Casio’s 3 August 2021 announcement placed both watches in its black-and-grey Master of G lineup and described their distinct series roles. Read Casio’s 2021 announcement for that launch positioning.
What features do they share?
Both official product listings specify shock resistance, 200-metre water resistance, a Carbon Core Guard structure, Bluetooth smartphone time adjustment and a CR2025 battery with approximately two years’ life. Each also lists step counting, an altimeter, a barometer, a digital compass and a thermometer.
Rank #2
- MUDMASTER Built for Extreme Environments – Rugged construction is engineered to resist mud, dust, shock, dirt, and debris, making the GG1000-1A5 ready for demanding outdoor conditions.
- Twin Sensor Compass & Thermometer – Built-in digital compass measures direction across 16 points and 0° to 359°, while the thermometer measures temperatures from 14°F to 140°F (-10°C to 60°C).
- Shock Resistant & 200M Water Resistant – Legendary G-SHOCK toughness combines shock-resistant construction with 200-meter water resistance for dependable performance during outdoor adventures and demanding work.
- Super Illuminator LED Backlight – High-brightness white LED backlight features an auto light switch, selectable 1.5- or 3-second illumination, and afterglow for improved visibility in low-light environments.
- World Time & Advanced Timekeeping – Includes world time across 31 time zones and 48 cities, a 1/100-second stopwatch, 60-minute countdown timer, 5 daily alarms, snooze alarm, and full auto-calendar through 2099.
That shared equipment means the decision is not a choice between a feature-rich watch and a basic one. The clearer distinctions in the specifications are the model’s series, additional stated resistance, size, weight and case/bezel material listing. The published water-resistance and battery-life figures are manufacturer specifications; they should not be read as a guarantee of performance in every use condition or of identical battery life for every owner.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Check the complete model code before buying
The title names the Mudmaster as GG-B100-8AER, but Casio’s Europe product page identifies the listed watch as GG-B100-8A. That page does not explain the “ER” suffix or establish whether it denotes a regional listing variant. Its specifications therefore apply to the GG-B100-8A Casio lists, not necessarily to every listing using a longer code.
Rank #3
![CASIO GWG-2000-1A1JF [G-Shock Carbon MUDMASTER Radio Solar Triple Sensor]Shipped from Japan](https://m.media-amazon.com/images/I/51QajkabT4L._SL160_.jpg)
- Item Trademark: Casio
- Item Category: Watch
- Manufacturer: CASIO
- Manufacturer: CASIO
Before ordering, compare the full model code shown by the seller with the code on the product packaging or watch documentation. The Gravitymaster’s listed model code is GR-B200-1B.
Quick Recap
Best Value
- Triple Sensor (compass, altimeter/barometer, and thermometer)
- Solar Powered
- Radio- Controlled
- Bluetooth Mobile Link
- Double LED
Rank #4
- Auto LED Super Illuminator
- Digital Compass
- Shock Resistant
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.
