Replacement 20x25x4 1/2 air filters for homes, offices, and commercial HVAC systems. 4½″ media cabinets are a common residential filter format designed for longer service intervals than 1″ or 2″ filters. Free shipping on orders over $50.

20+ years in filtration 4.8 from 1,000+ reviews

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  • 20x25x4-1/2 NaturalAire Choice Allergen MERV 8 82655.0452025 (2 Filters)
    MERV 8
    AAF Flanders

    20x25x4-1/2 NaturalAire Choice Allergen MERV 8

    $104.99
    $104.99
    Case of 2 $52.50/filter
  • 20x25x4-1/2 NaturalAire Optimum Allergen MERV 11 82755.052025 (2 Filters)
    MERV 11
    AAF Flanders

    20x25x4-1/2 NaturalAire Optimum Allergen MERV 11

    $145.99
    $145.99
    Case of 2 $73.00/filter

Commercial & facilities

Need 20x25x4-1-2 by the pallet?

Volume pricing on any size or MERV, plus recurring delivery schedules. We handle facilities and commercial orders daily and can usually match or beat distributor pricing.

Request a quote 1-866-469-8556 Talk to a filter expert

20x25x4 1/2 HVAC, Furnace & AC Filters

Replacement 20x25x4 1/2 air filters for homes, offices, and commercial HVAC systems. 4½″ media cabinets are a common residential filter format designed for longer service intervals than 1″ or 2″ filters. Free shipping on orders over $50.

If your rack is labeled 20x25x4 1/2, any filter here will fit. Actual dimensions vary slightly by manufacturer—check the product page for exact specs. Need a non-standard size? Our custom filters cut to 1/8″ precision.

Which MERV Rating Should I Choose?

  • MERV 8 (pleated) — Residential and light-commercial standard. Captures dust, pollen, lint, and mold spores.
  • MERV 10–11 — Captures pet dander, finer particulate, and some bacteria. Recommended for pets, allergies, and facilities pursuing better IAQ.
  • MERV 13 — Hospital-grade. Captures smoke, bacteria, virus carriers, and most airborne allergens. ASHRAE and CDC recommend MERV 13 where the HVAC system can support it.

Not sure? Take our MERV quiz or call 1-866-469-8556.

How Often Should I Change a 20x25x4 1/2 Filter?

4½″ media cabinets hold far more media than 1″ or 2″ filters, so they run much longer between changes—typically every 6–12 months. Fewer changes per year, less labor, and typically lower total cost of ownership. A 6-month or annual subscription matches the natural changeout cycle.

Why Buy From RememberTheFilter.com

  • Trusted brands — AAF Flanders, Koch, and our own PrimeShield line.
  • Filter Fit Guarantee — if it doesn't fit as expected, we'll make it right.
  • Free shipping over $50 to the lower 48, subscription discounts up to 10%, commercial & bulk pricing available.