A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 5975-01-432-1989
NSN 5895-01-444-1331
NSN 5998-00-113-9751
NSN 7035-01-158-7673
NSN 6645-00-115-3213
NSN 6685-01-516-4092
NSN 6620-01-095-8937
NSN 6685-01-615-7227
NSN 2925-01-569-5471
NSN 6320-01-106-4414
NSN 5960-01-499-3544
NSN 6685-00-901-2255