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20x20x1 Air Filters

20x20x1 is a square size that often sits behind a ceiling or wall return grille.

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20x20x1 is a square size that often sits behind a ceiling or wall return grille.

  • Actual size is about 19.5 x 19.5 x 0.75 in.
  • Grille mounting. In a return grille the filter is held by the hinged cover; the airflow arrow points into the duct, away from the room.
  • Rating. If your system was designed for basic fiberglass filters, stepping up to MERV 8 pleated is usually safe; ask an HVAC technician before going to MERV 13.

Not sure which rating to buy? See the MERV rating chart and the MERV finder. All sizes: HVAC and furnace air filters.