A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 6610-01-336-0484
NSN 5905-00-994-1947
NSN 5930-01-381-2143
NSN 6220-01-345-8655
NSN 5975-00-276-3436
NSN 5985-00-952-5519
NSN 5925-00-952-5824
NSN 5965-01-318-5836
NSN 5925-00-926-8425
NSN 5910-01-106-3261
NSN 5975-00-863-0704
NSN 5925-01-442-8589