FUEL TANK IN PLACE, THE LARGE 3" HOLE WITH THE X IS THE HEATED AIR WHICH WILL GET A 3" DUCT, THE LOWER PIPE IS THE COMBUSTION EXHAUST WHICH GOES INTO A STAINLESS FLEX TUBING AND IS COVERED WITH A WHITE ASBESTOS SHEATH SAFETY WIRED IN PLACE AND THEN PLACED INSIDE A TWO INCH FOIL DUCT TO HELP INSULATE FROM IT'S SUROUNDINGS