Whatever you’re doing, wherever you are — the G-SHOCK Master of G line has your back. 
Based on GRAVITYMASTER, MUDMASTER, and MUDMAN models that deliver peak performance in punishing conditions in the air and on land, this line features a black watch case symbolizing toughness, with accents in vivid emergency colors that capture the world of professionals involved in rescue efforts and other critical missions. 
The organic form of the GRAVITYMASTER GR-B300EC is inspired by next-generation aircraft and rendered with a seamless exterior design. The Carbon Core Guard structure and wide 3D face deliver durability, readability, and a comfortable fit. Enjoy all the practical functions as well, including dual-time simultaneously showing the time in two cities, a flight log memory function for recording routes traveled, and more.

Case / bezel material: Bio-based Carbon / Bio-based resin / Stainless steel
Bio-based resin band
Mineral Glass
Black ion plated bezel
Neobrite
Shock Resistant
Carbon Core Guard structure
Screw Lock Crown
200-meter water resistance
LED light (Super Illuminator)
Afterglow
LED:White
Tough Solar (Solar powered)
Mobile link (Wireless linking using Bluetooth®)
Dual time (Home City time swapping)
1-second stopwatch
Measuring capacity: 23:59'59.
Measuring modes: Elapsed time, split time
Countdown timer
Measuring unit: 1 second
Countdown range: 24 hours
Countdown start time setting range: 1 minute to 24 hours (1-minute increments and 1-hour increments)
Daily alarm
Battery level indicator
Power Saving (hands stop to save power when the watch is left in the dark)
Full auto-calendar (to year 2099)
Date display
Day indicator
Regular timekeeping:
Analog: 3 hands (hour, minute (hand moves every 10 seconds), second), 3 dials (dual time hour and minute, dual time 24-hour, day)
Accuracy: ±15 seconds per month (with no mobile link function)
Approx. battery operating time:
5 months on rechargeable battery (operation period with normal use without exposure to light after charge)
18 months on rechargeable battery (operation period when stored in total darkness with the power save function on after full charge)
Size of case : 59 × 54.7 × 15.7 mm
Total weight : 71 g