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21x21x1 Air Filter Merv 8
21x21x1 AC Filter Merv 11
21x21x1 Furnace Filter Merv 13
21x21x1 Filter Merv 13 Titanium
21x21x1 Filter Merv 10 Carbon
21x21x1 Filter Merv 8 Carbon 21x21x1 Filter Merv 8 Carbon
Protects All Against
  • Pollen protection
  • Dust protection
  • Mold protection
  • Dust Mites protection
    Dust Mites
  • Bacteria protection
  • Pet Dander protection
    Pet Dander
  • Smoke protection
  • Viruses protection
  • Cooking Smoke protection
  • Odor protection
  • Smog protection
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21x21x1 Air Filter

AC Furnace Air Filter 21x21x1 -Inches

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Odor Eliminator

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Product Description

Item Model Number: FKFB21X21
Brand: Filter King
Filter size: 21x21x1
Actual Size: 20.5 x 20.5 x .75
1-Inch Filter
MERV 8 Filter Rating
Protection From: Pollen, Dust, Mold, Dust Mites, Bacteria, Pet Dander, Smoke, Viruses
Residential / Commercial Use

Manufactured in the US

Why Buy Air Filters From Filter King?


In comparison to fiberglass filters, 21x21x1 pleated air filters are at least 20 times more effective. All Filter King air filters are made in the US.


Filters frames are made out of heat resistant paperboard with horizontal grid supports. Able to withstand temperatures of up to 200° F and resistant to moisture, the paperboard frames do not support microbial growth and outperforms traditional cardboard frames.


Chemical free, electrostatically charged synthetic polyester media is pleated, maximizing the surface area, to capture a high number of airborne particles as small as 0.3 microns with low air flow resistance. To increase durability, the media is supported with a corrosion resistant steel wire.

21x21x1 Air Filter Reviews

What MERV Rating should I choose?

How Often to Change Your 21x21x1 Air Filter?

Filter King AC & furnace filters aren’t the typical fiberglass filters that need to be replaced every 30 days. Our filters can typically be used for 3 to 5 months before requiring to be changed. Naturally, a variety of things influence filter lifespan.

Some of the factors that influence your filter’s life include outdoor air quality, whether pets are in the home, and how well your HVAC system is maintained.

Your air filter becomes clogged over time by trapped particles, preventing airflow. The efficiency of the HVAC filter declines. Your system must work harder to heat and cool your home. The extra strain on the HVAC system causes higher energy bills. Regular home air filter replacements can prevent expensive system repairs or replacements down the road.

You should change your filter more frequently if you notice:

  • Household dust build-up
  • The air isn’t cooling as is used to
  • There’s more dust near the air vents
  • A dirty filter surface
  • Higher energy bills
  • Burning smells near your HVAC system.

21x21x1 Air Filter

Filter King 21x21x1 size air filters are available for installation in order to keep the air coming through your home’s air systems clean. The filters in your home consist of a tight mesh weaving that is capable of capturing and absorbing irritants out of passing airflow. Your air filters will work constantly over time as airflow continues to enter your home. The process raises indoor air quality and keeps the air coming in comfortable and safe to breathe. Air filters are important tools for your home air systems, but they cause problems as they grow dirtier over time.

Your air filters grow dirtier the longer they are left in your air systems, which leads to several issues. The foremost problem being the fact that dirty air filters are unable to allow airflow to pass through easily. A lack of fresh airflow leads to dryness and stagnation throughout your home over time. Your air systems also suffer from the blockage, and attempt to push airflow through into your home. Air systems are strained as they try to push airflow forward leading to issues with mechanical damages and a rise in energy billing.

New air filters will help keep airflow coming into your home smoothly while also keeping it clean. Filter King offers fresh, new 21x21x1 size air filters available and ready for purchase. We also have a delivery service to have new filters brought right to you, our subscription option has new filters brought as often as monthly. Our air filters rate as an eight on the MERV (Minimum Efficiency Reporting Value) scale. This means that they filter out particles like:

  • Pollen
  • Dust
  • Mold
  • Dust Mites
  • Bacteria
  • Pet Dander
  • Smoke
  • Viruses

21x21x1 Furnace Filters

Furnace air filters are used in their systems to keep heated airflow clean as it travels through into your home. The filtration process is necessary to prevent allergens and pollutants from polluting your home. Furnace air filters will become dirtier over time, and dirty furnace filters block heated airflow from entering your home. The resulting issues with internal heating and temperature fluctuations only grow worse over time. Order new air filters to help keep airflow coming in without issue and prevent your systems from becoming damaged over time.