A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 5996-01-633-7979
NSN 5990-01-196-2953
NSN 5990-01-191-1772
NSN 6130-00-170-4844
NSN 6650-00-098-6128
NSN 5925-01-318-7846
NSN 6620-01-391-1920
NSN 6610-01-078-5270
NSN 5930-00-063-2003
NSN 5895-00-043-1155
NSN 5855-00-014-5008
NSN 5855-01-655-4035