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Need a different depth?

Same size, deeper filter

Below is 21x21 at 1 naturalaire″. A thicker filter holds more before it loads up, so it lasts longer between changes and puts less strain on the blower — we carry the same width and height in the depths below.

21x21x2 Built to order 21x21x4 Built to order

Ordering for a building? Ask for volume pricing or call 1-866-469-8556.

  • 21-1/4x37-1/4x1 NaturalAire Standard MERV 8 Filters (12 pack)
    AAF Flanders

    21-1/4x37-1/4x1 NaturalAire Standard MERV 8

    $297.99
    $297.99
    Case of 12 $24.83/filter
  • 18x21x1 NaturalAire Odor Eliminator with Baking Soda MERV 8 air filter
    MERV 8
    AAF Flanders

    18x21x1 NaturalAire Odor Eliminator with Baking Soda MERV 8

    $98.99
    $98.99
    Case of 4 $24.75/filter
  • 20x30x1 NaturalAire Healthy Ultra MERV 13 Filters (12 pack)
    MERV 13
    AAF Flanders

    20x30x1 NaturalAire Healthy Ultra MERV 13

    $228.99
    $228.99
    Case of 12 $19.08/filter
  • Naturalaire MERV 10 air filters custom size
    MERV 10
    AAF Flanders

    Custom Size NaturalAire Microparticle MERV 10 Air Filter

    $228.99
    $228.99
  • 22x22x1 NaturalAire Standard MERV 8 84858.012222 (12 Filters)
    MERV 8
    AAF Flanders

    22x22x1 NaturalAire Standard MERV 8

    $155.99
    $155.99
    Case of 12 $13.00/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
  • 22x22x1 NaturalAire Healthy Ultra MERV 13 Filters (12 pack)
    AAF Flanders

    22x22x1 NaturalAire Healthy Ultra MERV 13

    $213.99
    $213.99
    Case of 12 $17.83/filter
  • 20x22-1/4x1 NaturalAire Standard MERV 8 84858.01202225 (12 Filters)
    MERV 8
    AAF Flanders

    20x22-1/4x1 NaturalAire Standard MERV 8

    $173.99
    $173.99
    Case of 12 $14.50/filter
  • NaturalAire Healthy Ultra MERV 13 (4 Filters)
    MERV 13
    AAF Flanders

    NaturalAire Healthy Ultra MERV 13

    $100.99
    $100.99
    Case of 4 $25.25/filter
  • 14x18x1 NaturalAire Microparticle MERV 10 Filters (12 pack)
    MERV 10
    AAF Flanders

    14x18x1 NaturalAire Microparticle MERV 10

    $217.99
    $217.99
    Case of 12 $18.17/filter
  • 29-1/2x23-1/2x1 NaturalAire Standard MERV 8 Filters (12 pack)
    AAF Flanders

    29-1/2x23-1/2x1 NaturalAire Standard MERV 8

    $306.99
    $306.99
    Case of 12 $25.58/filter
  • 10x10x1 NaturalAire Microparticle MERV 10 Filters (12 pack)
    MERV 10
    AAF Flanders

    10x10x1 NaturalAire Microparticle MERV 10

    $116.99
    $116.99
    Case of 6 $19.50/filter
  • 12x24x1 NaturalAire Healthy Ultra MERV 13 95003.011224 (12 Filters)
    MERV 13
    AAF Flanders

    12x24x1 NaturalAire Healthy Ultra MERV 13

    $174.99
    $174.99
    Case of 12 $14.58/filter
  • 14x24x1 NaturalAire Healthy Ultra MERV 13 Filters (12 pack)
    MERV 13
    AAF Flanders

    14x24x1 NaturalAire Healthy Ultra MERV 13

    $248.99
    $248.99
    Case of 12 $20.75/filter
  • 16x24x1 NaturalAire Healthy Ultra MERV 13 Filters (12 pack)
    AAF Flanders

    16x24x1 NaturalAire Healthy Ultra MERV 13

    $203.99
    $203.99
    Case of 12 $17.00/filter
  • 10x30x1 NaturalAire Healthy Ultra MERV 13 Filters (12 pack)
    AAF Flanders

    10x30x1 NaturalAire Healthy Ultra MERV 13

    $300.99
    $300.99
    Case of 12 $25.08/filter
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