Adjustable flow control of air flow and direction for both heat and AC Easy installation with countersunk holes and screws for Size measurement is for duct opening not product dimensions Solid heavy duty metal air vent for ceiling register or sidewall register Hartford Ventilation Two Way Wall Vent Cover is and adjustable air vent cover for walls and ceilings. The multi-louver damper allows adjustment of both air flow and direction. To know correct size of wall vent, measure duct opening and select correct size. Hartford Ventilation Two Way Wall Vent Cover comes with a lifetime warranty.