Pauls Fisher-Price rocket heat riser mystery

Hi everyone,

I seem to have a dim memory of once hearing in a podcast that the heat riser in Paul's rocket mass heater in the Fisher-Price house was made from a fancy and secret material.
I think i also possibly hallucinated that Paul promised to reveal the nature of the super secret, super heat riser after two months of having people guess what it might be.

So did anything ever show up of this kind? I think the podcast was from around last new year.

It's vacuum formed ceramic stuff, the riser parts I believe are produced for pipe lagging, and the burn-tunnel was created from a mold they already had been using for small animal cremation. "the puppy cooker". Myself, would like to know if they have part numbers for these pieces, and if the company used was Fiberfrax. https://www.unifrax.com/fiberfrax-ceramic-fiber-products/

Thanks, that makes sense.