Abstract: A replaceable, self-spacing, pleated, filter insert that can be easily installed in a reusable filter frame without the aid of a secondary spacing structure includes reversibly collapsible and expandable filter media including a plurality of pleats that expand uniformly when the filter is expanded. When the filter is expanded to the length of the filter frame, the filter is under tension and behaves like a spring, thereby allowing the length of the filter to be readily adjusted to match the length of the frame and allowing the pleats to be aligned with corresponding ribs provided in the frame.

Abstract: A filter assembly includes a reusable filter frame and a replaceable, pleated, reversibly expandable, self-spacing filter removably arranged in the frame. The self-spacing pleated filter expands uniformly with equal pleat spacing to allow the filter to be easily installed in the reusable filter frame without the aid of a secondary spacing structure. When the filter is expanded to the length of the filter frame, the filter is under tension, thereby allowing the length of the filter to be readily adjusted to match the length of the frame and allowing the pleats to be aligned with corresponding ribs provided in the frame.