The present disclosure generally relates to air filters expandable from a collapsed arrangement to an expanded, end-use arrangement and to methods of making, using, and installing such air filters. Some embodiments relate to an air filter having an expanded state and a collapsed state. The air filter includes a filter media assembly including (1) filter media including a plurality of pleats, (2) first and second opposing sides, and (3) first and second opposing ends. The air filter also includes a shape retention structure capable of being connected to at least a portion of the filter media assembly and capable of retention the filter media assembly in the expanded state. A spacing distance between adjacent pleats in the filter media is greater in the expanded state of the air filter than in the collapsed state of the air filter. In some embodiments, the air filter is an HVAC air filter.