A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 4140-00-169-3549
NSN 5905-01-120-4917
NSN 5855-01-612-7608
NSN 6220-01-494-0572
NSN 6150-00-236-5069
NSN 5975-01-114-4625
NSN 6645-01-486-1139
NSN 5950-00-648-6534
NSN 7035-00-096-9986
NSN 2925-01-294-0585
NSN 6145-01-275-1214
NSN 6620-01-542-8709