Filter King FKFA20X21A-6 20×21×1-Inch MERV 11 Air Filters, 6-Pack

Filter King FKFA20X21A-6 is a six-pack of MERV 11 pleated filters listed for air conditioners and furnaces. The nominal 20×21×1-inch size is not the stated actual thickness, so match the actual dimensions to your filter slot before ordering.

At a glance

The listing distinguishes a nominal 20×21×1-inch filter size from an actual size of 20 × 21 × .75 inches.
The seller recommends replacing one-inch filters every 30 to 90 days. It says filters can last up to 90 days.
Pleated construction and slide-in mounting are listed.

Price

$67.98Save 25%

Reference price: ~~$90.72~~

Price checked: Nov 14, 2026

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Pros and cons

Pros

Six filters in one pack provide replacements for successive change intervals.
The listing provides both nominal and actual dimensions, useful when checking fit.

Technical specifications

10 specifications

Identity
Brand	Filter King
Model	FKFA20X21A-6

Dimensions and installation
Dimensions listed	21"L x 20"W x 0.75"Th
Mounting type	Slide In
Shape	Rectangular

Materials and protection
Material listed	Polypropylene
MERV rating	11

Compatibility and quantity
Compatible devices	Air Conditioner, Furnace
Compatible HVAC systems	residential
Quantity	6

What to know before buying

Listing details to confirm

The listed dimensions show 0.75-inch thickness, while the title and description use a nominal 1-inch size. Measure the existing filter and confirm the slot accommodates the stated actual dimensions. The source recommends 30–90-day replacement intervals and claims up to 90 days, depending on use.

What’s in the box

Included

Air filters (6)

Who is it for?

A good fit for

Households replacing a residential air-conditioner or furnace filter that matches the stated actual dimensions.
Buyers seeking a MERV 11 pleated filter in a six-pack.

Filter King FKFA20X21A-6 20×21×1-Inch MERV 11 Air Filters, 6-Pack · photo 2 — Additional product photo 2

Customer reviews on Amazon

4.2 / 5 · 31 ratings

5 stars69%69%
4 stars10%10%
3 stars6%6%
2 stars4%4%
1 star11%11%

Aggregate ratings lean positive, with five-star ratings forming the largest share, but a notable one-star share shows that ratings are not uniformly favorable. Without customer comments, the reasons behind either positive or negative ratings are unknown. Treat the ratings as limited context, not evidence of specific filtration performance or fit. Confirm the actual dimensions for your system.

Frequently asked questions

What are the stated actual dimensions?

The listing gives 20 × 21 × .75 inches as the actual size, while presenting 20×21×1 inches as the nominal size. Check your existing filter and slot before ordering.

How often does Filter King recommend replacing the filter?

The listing recommends changing one-inch filters every 30 to 90 days and says this filter can last up to 90 days. Actual replacement timing may depend on use.

Which systems is this filter listed for?

The listing names air conditioners and furnaces and specifies residential HVAC systems.