A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 6105-01-634-0322
NSN 5915-00-733-3694
NSN 4140-01-066-6891
NSN 6135-00-209-6918
NSN 6650-01-015-1589
NSN 5990-01-089-9694
NSN 6610-01-065-1073
NSN 5965-01-003-2641
NSN 6135-01-468-6491
NSN 6130-01-417-7589
NSN 6620-01-054-9346
NSN 6620-01-032-3937