This invention provides an improved construction for air filters wherein the filter frame is provided with indentations or recesses adjacent to its opposite corners which allow a plurality of filters to nest together in a laterally offset relationship to conserve space. The invention can be employed with an air filter including a filter element of fibrous material and a frame for supporting the filter element at its marginal edges. Preferably, a set of recesses is formed in the filter frame at positions adjacent to its diagonally opposite corners. Each recess is adapted to receive the frame of another air filter to permit the filters to nest together in a laterally offset relationship for shipment or storage. The air filters are arranged in a stack with alternate filters in the stack diagonally displaced relative to the remaining air filters. The recesses permit each air filter to be nested with one or both of its neighbors.