This HEPA Exhaust Filter fits in a door on the side of the Hoover Windtunnel upright vacuums. It consists of fanfold filter media in a white plastic cartridge. The cartridge measures 10 15/16" x 3 3/8" x 1/2". A seal around its edge ensures that the air passes through it, not around it like the Genuine Hoover version. This design provides a large filter media area for reduced resistance to air flow while producing a high level of filtration which meets the stringent HEPA specification for the air that passes through it. This filter is interchangeable with the WindTunnel Exhaust Filter with Seal #43613021 and WindTunnel HEPA Exhaust Filter #43613022 . For similar products see our list of Hoover Vacuum Supplies.