Abstract: An adjustable filter assembly for a variety of filtration applications. The adjustable filter assembly includes a fixed-size filter medium and frame and an adjustable molding for adjustably applying said filter assembly in applications having widely varying dimensions. The filter assembly can take a variety of shapes and sizes so that any vent may be adequately fitted and filtered. The adjustability of the assembly is accomplished by the molding having at least one adjustable joint enabling the molding to be continuously adjusted from an unextended position through to a fully extended position. In the unextended position, the outside edge of the molding coincides with the perimeter of the filter media and the inner edge of the molding defines a minimum exposed area for the filter medium. In the fully extended position, the inner edge of the molding coincides with the perimeter of the filter media and the outside edge of the molding extends outwardly significantly beyond the perimeter of the filter media.