4" MERV 13 Furnace & AC Air Filter by Filters Fast® - 3-Pack
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  • Size Actual Dimension
  • 12x24x4 11.375" x 23.375" x 3.625"
  • 16x20x4 15.5" x 19.5" x 3.625"
  • 16x25x4 15.5" x 24.5" x 3.625"
  • 18x24x4 17.375" x 23.375" x 3.625"
  • 20x20x4 19.5" x 19.5" x 3.625"
  • 20x24x4 19.375" x 23.375" x 3.625"
  • 20x25x4 19.375" x 24.375" x 3.625"
  • 24x24x4 23.375" x 23.375" x 3.625"
  • 25x29x4 24.375" x 28.375" x 3.625"
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4" MERV 13 Furnace & AC Air Filter by Filters Fast® - 3-Pack


Only $30.98 per Filter
Retail: $119.99 /ea
You Save: 23%
As low as
Retail: $119.99
You Save: 23%
4 MERV 13 Air Filter Sizes :
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The Filters Fast® 4-inch Air Filters (FFM136) have a MERV 13 rating and are useful in a variety of settings, including homes, offices, and industrial sites. These MERV 13 filters effectively reduce pollen, dust, pet dander, mold spores, and dust mites, as well as bacteria, smoke, smog, and other allergens. The higher quality construction from these 4-inch filters benefits health and respiration, including alleviating problems with allergies and sinus irritation that might lead to itchy throat, watery eyes, coughing, and sneezing. 4-inch air filters are also more effective than thinner filters because their larger surface areas are much more durable. Filters Fast® air filters are affordable without sacrificing quality. These HVAC air filters arrive in a variety of sizes to meet your air quality needs.

Note: These filters do not contain fiberglass.


  • Brand: Filters Fast®
  • Part Number: FFM136, Ffm1362
  • Pack Size: 3
  • Filter Life: 6 - 12 months
  • MERV Rating: 13

Available Sizes:

The 4" MERV 13 Furnace & AC Air Filters by Filters Fast® are available in the following sizes:

Nominal Size Actual Size Alternate Part Number
12x24x4 11.375x23.375x3.625 PF13.0412243PFF, ffm136-12244
16x20x4 15.375x19.375x3.625 PF13.0416203PFF, ffm136-16204
16x25x4 15.375x24.375x3.625 PF13.0416253PFF, ffm136-16254
18x24x4 17.375x23.375x3.625 PF13.0418243PFF, ffm136-18244
20x20x4 19.375x19.375x3.625 PF13.0420203PFF, ffm136-20204
20x24x4 19.375x23.375x3.625 PF13.0420243PFF, ffm136-20244
20x25x4 19.375x24.375x3.625 PF13.0420253PFF, ffm136-20254
24x24x4 23.375x23.375x3.625 PF13.0424243PFF, ffm136-24244
25x29x4 24.375x28.375x3.625 PF13.0425293PFF, ffm136-25294

Please note that if you are unsure whether you need an actual or nominal size simply measure your air filter before placing your order.

Custom Sizes:

  • If you don' t see your size, order a custom made air filter! Custom made air filters do not come individually wrapped.

How do you install the 4" MERV 13 Furnace & AC Air Filter by Filters Fast®?

  1. Once your air filters arrive, gather your supplies including a ladder (if needed,) safety goggles, gloves, a mask, and a disposable bag.
  2. Remove the metal grate from your air return.
  3. Carefully remove the used air filter and place it immediately and gently into the disposable bag. Then tie the bag sealed.
  4. Place the new air filter in place of the filter you just removed and replace the metal grille.

How often should you replace the 4" MERV 13 Furnace & AC Air Filter by Filters Fast®?

  • Changing your 4" MERV 13 Furnace & AC Air Filter by Filters Fast® is a very quick and easy process that should be done once every six to twelve months.

What contaminants does the 4" MERV 13 Furnace & AC Air Filter by Filters Fast® reduce?

  • The 4" MERV 13 Furnace & AC Air Filter by Filters Fast® is a MERV 13 air filter, which means that it reduces the following contaminants:

    • Dust
    • Pollen
    • Mold Spores
    • Bacteria
    • Pet Dander
    • Dust Mites
    • Smoke & Smog
    • Virus Carriers
    • Other Common Airborne Allergens


Customer Reviews:

Total Reviews: 61 Average Rating: 4.8 / 5.0

Filtersfast Reviews on Trust Pilot external site
Dale Van Pelt2024-02-29

Good for homes with asthma and pets

Collected by Trustpilot.com
James Marshall2024-02-20

Too soon to tell regarding comparitive quality/value

Collected by Trustpilot.com

seems to be a good product

Collected by Trustpilot.com
Nathan Hockett2024-02-03

They didn't fit my furnace. The size stated was less than my filter praying the furnace. Although my furnace tray is the same size statedthat the filters were. The filters are not. Although filters fast said just keep em. We'll refund your money. I need check to ensure it was refunded. I'm sure they'll work as mfg'd in a furnace filter they'll actually fit. But they were not 20x20x4 inches as stated.

Collected by Trustpilot.com

Good quality. Good customer service.

Collected by Trustpilot.com
Susan Komenda2024-01-05

This product is what i need for my furnace. Came in one box and was in fine condition.

Collected by Trustpilot.com

These filters were described as being 4 inches thick. They are only 3.5 inches. I should have bought them in a local store where I could see them in person before purchase.

Collected by Trustpilot.com
John P Jones2023-07-31

Keeps the house clean

Collected by Trustpilot.com
Gene Molloy2023-07-24

MERV 13 is a little better than most homeowners would use in a residential setting, but I'm a go for the gusto extremist, and a retired Stationary Engineer, who knows the value of a good preventive maintenance program, and good filtration. These are the best I've found.

Collected by Trustpilot.com

The best easiest to install filters we’ve ever used

Collected by Trustpilot.com

We feel that the air quality is very much better than earlier selection.

Collected by Trustpilot.com

Works great Good Price

Collected by Trustpilot.com
Rich P2023-06-19

The right size and quality when I need it.

Collected by Trustpilot.com
EUGENE R Everett Jr.2023-06-10

Works as expected

Collected by Trustpilot.com

Fast delivery service. Easy website to navigate. Better price than my local stores.

Collected by Trustpilot.com

Great experience

Collected by Trustpilot.com
Lynn Kroonblawd2023-05-18


Collected by Trustpilot.com
Lynn Colburn2023-05-05

I have been using these for years and they do quite well. They are an affordable and well made filter.

Collected by Trustpilot.com

Very good Air Filters

Collected by Trustpilot.com
Tim M.2023-03-18

Good stuff!!! Easy to order. Prompt delivery. See

Collected by Trustpilot.com

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