Dragon Glass 1/4" Reflective Fire Glass, 25 lb, Copper Glass will not melt, degrade or produce toxic fumes Glass size -1/4 " or 7-12 mm 0.33 cu. ft. bag, coverage area 1.16 sq. ft Rectangular fireplace / fire pit (length x depth x glass height) / 19 = glass (lbs.) Round fireplace / fire pit (diameter x diameter x glass height) / 24 = glass (lbs.)