No, it should be outer diameter.
Perlite refractory brick is classified to outer diameter and inner diameter, pay attention to the accuracy of the size when measures, after drying, contains refractory. Our clay refractory bricks use 50% soft clay and 50% flint clay clinker, sodium to blend together according to a certain granularity requirements, after molding, etc., fireclay brick, 3373 in fact, there are many kinds of refractory bricks.
