Abstract: A foldable filter frame is provided. The filter frame includes a filter media panel and a rectangular support frame surrounding the filter media panel. The support frame included four edge elements. Each edge element has a double-walled construction and is foldable into a position in which a first leg of the respective edge element is generally perpendicular to a second leg of the edge element. An end of at least one of the edge elements that defines a corner of the support frame supports a foldable tab that is receivable in a complementary slot in an end of the other edge element defining the respective corner of the support frame with the tab being arranged in an inner space between the double-walls of the edge element.