COMBUSTION EXHAUST IN STAINLESS STEEL COVERED WITH WHITE SHEATH SAFETY WIRED AT EACH END, THEN PUT INSIDE 2'' DUCT FROM HEATER TO THRU HULL. THE HEATED AIR DUCT WAS CONVERTED FROM 2" TO 3" BY CHANGING THE END CAP ON THE HEATER,WILL ADD Y SO I CAN GET A DUCT UP TO THE WINDSHIELD AND OR TO THE BERTH AREA