A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 6645-00-851-6654
NSN 6650-01-217-0303
NSN 6240-01-294-3465
NSN 5895-00-653-4227
NSN 5965-01-263-8601
NSN 5960-01-430-3911
NSN 5895-01-597-6406
NSN 5895-00-793-7956
NSN 6150-01-650-4631
NSN 6135-01-388-2761
NSN 5910-00-362-6687
NSN 6685-01-459-5047