A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 4140-01-077-3981
NSN 6650-00-738-5418
NSN 6150-00-218-0891
NSN 6645-01-504-3394
NSN 6130-00-654-5833
NSN 5998-01-323-6084
NSN 4140-01-015-5137
NSN 5930-01-427-3676
NSN 5935-00-477-4782
NSN 5835-01-641-0073
NSN 5990-00-630-6154
NSN 5905-00-660-5615