A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 5990-00-321-8459
NSN 6620-01-603-6442
NSN 6650-01-228-5094
NSN 5895-00-173-4676
NSN 5965-01-231-9125
NSN 6645-00-888-5820
NSN 5990-01-512-9129
NSN 5996-01-463-8197
NSN 7035-00-562-9881
NSN 6145-01-350-3264
NSN 5975-01-019-9472
NSN 6645-01-489-5426