An air return filter or air supply grille assembly having an interchangeable perforated face plate hingedly attached directly to a molded fiberglass plenum. The molded fiberglass plenum has a preformed recess for receiving and positioning a filter resting on the face plate when used as an air return filter grille assembly. The hinge system for the interchangeable perforated face plate is comprised of a pair of mating half hinges with one half secured to the plenum and the other half secured to each interchangeable face plate. The grille assembly can be mounted and a perforated face plate selected to provide an air return filter grille assembly or an air diffusing supply grille assembly. The air filter grille assembly is constructed to mount easily on T-bar suspended ceilings with the perforated face plate held closed by manually rotatable pawls.

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return fifter qrille