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Round carbon case with black analog dial, bio-based resin strap, 59 by 54.7 mm

CASIO

CASIO G-SHOCK GRAVITYMASTER GR-B300-1A watch

SKU CH-J6C3-XW0Q5

A carbon-core solar watch with Bluetooth-linked world time and flight-log functions, 200 m water resistance and a bio-based resin strap

  • StyleSports
  • MaterialCarbon
  • MovementSolar
  • ShapeRound
  • Dial ColorBlack
  • Dial MarkersIndex With Numbers At 12 & 6 O'Clock
  • Carbon Core Guard case for lightweight strength
  • Tough Solar charges from any light source
  • Bluetooth Mobile Link enables automatic time sync
  • Bio-based resin components reduce environmental impact
  • 200 m water resistance suits professional marine use

Carbon Core Guard structure

The GRB300-1A is a GRAVITYMASTER aviation watch built for pilots and professionals who demand durability. Its Carbon Core Guard case uses carbon fibre-reinforced resin to deliver high strength with low weight. Tough Solar charging and Bluetooth Mobile Link provide automatic time correction and smartphone-based settings control. Water resistance is rated to 200 metres.

Tough Solar power reserve

The solar movement charges from any light source, giving months of operation in darkness after a full charge. Bluetooth connectivity handles world time updates and flight log management without button-heavy menus. The analog display with Neobrite hands and index markers at 12 and 6 o'clock remains legible in low light. The mineral crystal resists everyday scratches.

Bio-based resin construction

Key components including the case, bezel and strap use bio-based resin derived from renewable resources, reducing reliance on fossil plastics. The 59 by 54.7 millimetre case sits securely on a resin band with a buckle clasp. Buyers who need a lighter titanium case or a sapphire crystal should consider other ranges. This model suits those prioritising solar autonomy and cockpit-inspired readability.

Highlights

  • Carbon Core Guard case for lightweight strength
  • Tough Solar charges from any light source
  • Bluetooth Mobile Link enables automatic time sync
  • Bio-based resin components reduce environmental impact
  • 200 m water resistance suits professional marine use

Specifications

BrandCASIO
StyleSports
MaterialCarbon
MovementSolar
ShapeRound
Dial ColorBlack
Dial MarkersIndex With Numbers At 12 & 6 O'Clock
DisplayAnalog
DateDate
Band MaterialResin
FastenerBuckle Clasp
GenderMale
AgeAdult
ConditionNew
BezelFixed Bezel
Case MaterialCarbon
Case Thickness54.70 mm
CrystalMineral Crystal
Water-Resistant200m
Special FeaturesMineral Crystal,Buckle Clasp,Day and Date Display

Questions about this item

Will the carbon core guard structure and 54.7 mm case thickness sit comfortably under the cuff of a standard flight jacket sleeve?

The carbon core guard structure keeps the case lightweight while the 54.7 mm thickness and 59 mm width maintain a low profile that slides easily under most aviation jacket cuffs without snagging.

How do I confirm the tough solar charging and Bluetooth mobile link are active after the initial setup?

Place the watch in bright light; the power indicator will show charge level. Open the G-SHOCK Connected app — a successful pairing displays the current world time and flight log sync status on the phone screen.

Which items are included in the box and what must be purchased separately for full functionality?

The box contains the GR-B300-1A watch with bio-based resin strap, buckle clasp, mineral crystal, and documentation. A compatible smartphone running the G-SHOCK Connected app is required for Bluetooth mobile link features.

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