FIBRE-METAL F300 HEADGEAR WITH 3 INCHES CROWN RATCHET HEADBAND ACCOMMODATES 8 INCHES X 11 1/2 INCHES WINDOWS AND SUITS EASILY INTO SPECTACLES WITH SPACE FOR AIR CIRCULATION TO AVOID FOGGING. THIS FREE FLOATING HEADGEAR RESISTS HEAT AND FEATURES A SLOT/PIN MECHANISM WITH LOCKING CAMS. THE CHANNEL GRIP SYSTEM MOUNTS WINDOWS AND GRIPS THEM IN PLACE IN A DEEP RECESSED CHANNEL TO SECURE FROM DIRT AND DEBRIS.