I might be off on my terms or buck stove is off. I'm guessing it is me. There is a sheet of metal just above the secondary tubes that is about 1/4" thick. On top of that is the insulation. The sheet of metal is warped from the heat. I ordered a new one, or so I thought, from buck stove. The sent me a white, more rigid insulation. What is the plate called just above the secondary tubes on the buck stoves?