Ruskin ADR and ADF access doors are an inexpensive and trouble-free way to gain access into sheet metal ductwork systems for resetting dampers, cleaning filters, or access for general maintenance. The oval shaped opening permits the back plate or "inner plate" to be easily passed through the duct openings, and the neoprene gasket on the inner plate provides for an absolutely air-tight seal. The large hand knobs insure a quick method to remove and reinstall the door without the use of special tools. The ADR (for round duct work) and ADF (for flat duct work) are available in three sizes, 16" x 12", 10" x 6" and 8" x 4" to accommodate the many different sizes of duct work that are available.