Our return air grilles with or without filter are manufactured by injection molding from ABS engineering plastic. This material is corrosion-resistant. Insulating properties of ABS plastic prevent condensation making it ideal suitable for use with air conditioning systems both cool and heat (temperature range 0 to 65 °C / 30 to 140°F). The attractive return air grilles blend in with room décor and can be mounted on the wall or the ceiling. Standard color is glossy off-white; other colors can be supplied for large quantities..