Dragon Glass 1/2" Reflective Fire Glass, 10 lb, Bronze Glass will not melt, degrade or produce toxic fumes Glass size -1/2&quot; or 12-20 mm 0.125 cu. ft. bag, coverage area .47 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.)