Georgia-Pacific's DensArmor Plus Fireguard C Interior Gypsum Drywall Boards are dimensionally stable gypsum core is reinforced with glass fibers, increasing its strength and fire resistance. ToughRock Fireguard-C Gypsum Board is manufactured to meet ASTM C1396 Section 5. The 1/2 in. ToughRock Fireguard C is UL Type TG-C and ULC classified Type C.