Casio G-Shock Carbon Core Guard Analog Digital Quartz Diver's GA-2100-1A GA2100-1 200M Men's Watch The Carbon Core Guard structure takes the famous G-Shock toughness to a whole new level. The fine resin incorporates carbon fiber to make a tough yet light weight material with the kind of rigidity far more superior to that of usual resin. It is now more resistant to damages and deformation, eliminating the need for external button guards. Everything about it reeks of a bold toughness.