This Video is not the Caliber of Jurassic Park or Avitar but it kinda helps a little to give insight as to how the rocket stove works and a really good material to use in the fabrication. The intense heat generated by the Rocket Stove is in the range of 1,500*-and 2,000* F at the elbow of the J Tube. This causes the steel to burn up over the course of a year or a little longer. I went to a local Firebrick supplier and tried several different products and here is My second attempt. A lot of people I see are using 1/4" schedule 40 steel pipe to make them out of. Once they are encased in cob they are very hard to replace, so I figured I'd do it this way and avoid that. The second half is the one I built out of a very lightweight furnace insulation board. It works famously, although I have to change out the upper part of the exhaust with a heavier cast pipe, due to the board delaminating.