Used to regulate air by twisting handle to open and close damper. Install in black flue pipe. Used to regulate air by twisting handle to open and close damperInstall in black flue pipedesigned to control airflow and burn of the fire for greater heating efficiencyImperial's cast iron dampers are used to regulate the air by twisting the handle to open and close the damper. This damper should be installed in black flue pipe.