This specification covers alumina-silica, glass, and other ceramic fiber thermal insulation in the form of felt and fabric flat sheets, rolls or molded non-pliable blocks. Nominal thickness is 0.1 to 2.0 inches (3 to 51 mm) and nominal density is 2 to 24 pounds mass per cubic foot (32 to 384 kg/m3). This insulation has been used typically to provide thermal insulation at continuous hot-face temperatures from 500 to 2300 degrees F (260 to 1260 degrees C), but usage is not limited to such applications.