These are three identical air filters. They have a white plastic rectangular shell with openings at front and back. There is an arrow molded into the shell indicating the direction of airflow (front is the source of the air, back is the destination). They each have a black strip of foam around the edges of the back side to seal them. They each originally had a foam filter across the front which was disintegrating and has been removed. The inside is filled with an alternating sandwich of white foam and corrugated metal foil across the width.
