This WindTunnel Bagless Secondary Filter fits below the Twin Chamberô Dirt Container. It is visable throught the hole in its cover plate. The filter measures 5 5/8" x 2 1/2" x 1/4" with rounded ends. There is a 3/8" hole in the center through which the cover plate screw passes. While the earlier filters were green as shown, Hoover's later ones are white.