These registers and return grilles are to be installed in a 4 x 20 vent opening. Most vent coverings either come with the damper (or louver) to control airflow or you can add them if needed.
These registers and return grilles are to be installed in a 4 x 20 vent opening. Most vent coverings either come with the damper (or louver) to control airflow or you can add them if needed.