A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 6645-00-308-4179
NSN 5975-01-517-2938
NSN 5920-00-445-3585
NSN 6320-01-476-0686
NSN 4140-00-111-3247
NSN 5960-01-074-9388
NSN 6105-00-530-0656
NSN 6150-00-840-9424
NSN 5999-01-341-2363
NSN 2925-01-016-3111
NSN 5985-01-634-0635
NSN 6145-01-532-2042