A brick having a low thermal conductivity and used as a backing for the more dense refractory brick.
NSN 6620-01-423-7300
NSN 6220-01-587-9932
NSN 5965-01-364-1232
NSN 6610-00-726-0247
NSN 5999-01-193-5374
NSN 5950-01-320-6410
NSN 5950-01-078-4137
NSN 5920-00-554-0437
NSN 6240-01-431-5442
NSN 6145-01-504-4252
NSN 6135-01-215-1245
NSN 6620-01-118-7588