A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 4140-00-578-7726
NSN 6105-00-719-9943
NSN 6645-01-332-8982
NSN 5835-00-185-4919
NSN 6105-01-496-8659
NSN 5999-00-644-2854
NSN 5905-01-661-0578
NSN 6145-01-099-2682
NSN 5945-00-225-8421
NSN 6150-00-769-5017
NSN 5930-01-363-4417
NSN 5925-00-435-3849