A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 5960-00-474-8254
NSN 5925-01-609-8535
NSN 5998-01-064-6170
NSN 5990-01-205-5937
NSN 5985-00-673-1719
NSN 6645-01-534-5545
NSN 5960-01-487-6436
NSN 6220-01-172-9369
NSN 6135-01-136-8306
NSN 5915-01-555-9106
NSN 4140-01-179-8299
NSN 6610-01-512-2025