# Filter King FKFD21X21-12 21x21x1 MERV 13 Air Filters, 12-Pack

Filter King FKFD21X21-12 is a 12-pack of MERV 13 replacement filters listed for 21x21x1 AC and furnace applications. The listing gives the actual size as 20.5 x 20.5 x .75 inches, so confirm those measurements against your filter slot before ordering.

- [Original product page](https://best-deals.pro/product/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [View offer](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- Market: US
- Language: en-US
- Currency: USD
- Brand: Filter King
- Model: FKFD21X21-12
- Category: Home & Kitchen > Appliance Parts & Accessories > Air & HVAC Filters
- Price: 126.58 USD
- Previous price: 154.68 USD
- Discount: 18%
- Price checked: 2026-11-14T19:15:46.519Z
- Rating: 4.5 / 5
- Reviews: 178

Prices and deal status are the latest recorded data, not a guarantee of availability. Confirm the price and availability with the store.

## At a glance

- MERV 13 pleated filter, according to the listing.
- Listed for residential air conditioners and furnaces, with slide-in installation.
- The manufacturer recommends replacing 1-inch filters every 30 to 90 days and says these can last up to 90 days.

## Pros

- A 12-pack provides multiple replacements for recurring filter changes.
- The listing provides both nominal and actual dimensions, useful for checking fit before purchase.
- The stated MERV 13 rating and AC/furnace compatibility make the intended application clear.

## Specifications

### Identity
- Brand: Filter King
- Model: FKFD21X21-12
### Filtration and compatibility
- MERV rating: 13
- Compatible devices: Air Conditioner, Furnace
- Compatible HVAC systems: residential
- Shape: Rectangular
- Mounting type: Slide In
### Dimensions and installation
- Listed dimensions: 21"L x 21"W x 0.75"Th
- Advertised nominal size: 21" x 21" x 1"
- Actual size: 20.5" x 20.5" x .75"
### Materials and pack size
- Material: Polypropylene
- Quantity: 12

## Before you buy

- The listing gives a nominal size of 21 x 21 x 1 inches and an actual size of 20.5 x 20.5 x .75 inches. Customer feedback also includes mixed size and fit reports, including concerns that the size differs from 15.75 x 15.75 inches and that fit can be loose. Verify your slot dimensions and the selected listing details before ordering.

## In the box

- Air filter \(12\) (Included): The manufacturer contents list names an air filter, and the product listing identifies a 12-pack.

## A good fit for

- Households whose filter slot accepts the listed actual dimensions and uses a compatible residential AC or furnace.
- Buyers looking for a multi-filter supply with a stated MERV 13 rating.

## Less suited to

- Buyers who have not checked their filter slot dimensions or need a filter with a different actual size.

## Customer feedback

Customer feedback describes the filters as effective and good value, while reports about size and fit are mixed, including concerns about loose fit and a size differing from 15.75 x 15.75 inches. For buyers, that fit uncertainty matters because this product is listed at 20.5 x 20.5 x .75 inches actual size. The rating distribution is mostly five-star but includes lower ratings, so the aggregate does not resolve fit for a particular system.
- Positive themes: Customers report that the filters work well.
- Positive themes: Customers describe them as good value.
- Negative themes: Some customers report a loose fit or a size that differs from 15.75 x 15.75 inches.
- Mixed feedback: Customers disagree about whether the size fits as expected.

## Frequently asked questions

### What is the actual size of this filter?
The listing states 20.5 x 20.5 x .75 inches actual size, compared with a nominal 21 x 21 x 1 inches. Check these measurements against your filter slot.
### How many filters are included?
The product is listed as a 12-pack.
### How often should the filter be changed?
The manufacturer recommends changing 1-inch filters every 30 to 90 days and claims this filter can last up to 90 days. Actual replacement timing depends on your usage and conditions.
### What do customers report about fit?
Feedback is mixed. Some customers say the size is right, while others report size differences and a loose fit. Compare the stated actual dimensions with your existing filter and slot.

## Offer details

- The advertised 5% coupon is available when selecting Subscribe & Save.

## Alternative options

- [Simply 20x23x1 Air Filter, Merv 8, 12 Pack, For Home AC Furnace & HVAC \(Actual Size: 19.56"x22.56"x0.75"\) DUST, Pet & Allergy Control,](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Filterbuy 21x22x1 Air Filter MERV 8 Dust & Allergy Defense \(6-Pack\) \| Electrostatic Pleated HVAC AC Furnace Filters Replacement, Made in USA \(Actual Size: 20.50 x 21.50 x 0.75\)](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Simply 22x22x1 Air Filter, Merv 8, 6 Pack, Furnace Air Filter for HVAC \(Actual Size: 21.75"x21.75"x0.75"\) DUST, Pet, & Allergy Control](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Filter King 20x20x2 Air Filter MERV 11, AC Furnace Filters \(6-Pack\) \| Dust & Allergy Control \(Actual Size: 19.5 x 19.5 x 1.75\)](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Simply 20x21.5x1 Air Filter, Merv 8, 4 Pack, For Home AC Furnace & HVAC \(Actual Size: 20x21.5x0.75"\) DUST, Pet, & Allergy Control](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Simply 20x20x1 Air Filter, MERV 13, 12 Pack, For Home AC Furnace & HVAC \(Actual Size: 19.75"x19.75"x0.75"\) DUST, Pet, & Allergy Control](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Filterbuy 17.5x27x5 Air Filter MERV 13 Smoke & Allergy Defense \(2-Pack\) \| Pleated HVAC AC Furnace Replacement for Trane Perfect Fit & American Standard \(Actual Size: 17.13 x 26.13 x 4.97\)](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Aerostar Air Filter 21x21x1 MERV 8 AC Filter, HVAC, Furnace Filter, 6 Pack \| ACTUAL SIZE \(20.88 x 20.88 x 0.75\) AC Filter, HVAC, Furnace Filter Captures Dust, Lint & Pollen MERV 8](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [21 1/2 x 23 1/2 x 1 Air Filter Frame w/ High Flow Washable Media \| Compatible with ...](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Filter King 10x20x1 Air Filter MERV 13, AC Furnace Filters \(4-Pack\) \| Dust & Allergy Control \(Actual Size: 9.5 x 19.5 x .75\)](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Filter King 12x30x1 Air Filter MERV 13, AC Furnace Filters \(6-Pack\) \| Dust & Allergy Control \(Actual Size: 11.5 x 29.5 x .75\)](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Filter King 20x23x1 Air Filter MERV 8, AC Furnace Filters \(12-Pack\) \| Dust & Allergy Control \(Actual Size: 19.5 x 22.5 x .75\)](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)

## Add-ons

- [Filter King 20x20x1 Air Filter MERV 8, AC Furnace Filters \(12-Pack\) \| Dust & Allergy Control \(Actual Size: 19.5 x 19.5 x .75\)](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)
- [Filter King 18x30x1 Air Filter MERV 8, AC Furnace Filters \(6-Pack\) \| Dust & Allergy Control \(Actual Size: 17.5 x 29.5 x .75\)](https://best-deals.pro/visit/filter-king-fkfd21x21-12-merv-13-air-filter-12-pack)

## Images

![Filter King FKFD21X21-12 21x21x1 MERV 13 Air Filters, 12-Pack — 1](https://best-deals.pro/i/1TJrs7M4bCiIWNzn8oT_Ejucs780zkEof_1ZidEif_paME-Q5OyHaLmnzxoGnP_IpFewvFjChvh7fTWcoCqrdbi5ZMwoWfhGWLVHx2Kz4_nvMLi2WpZFVMjA.jpg)

![Filter King FKFD21X21-12 21x21x1 MERV 13 Air Filters, 12-Pack — 2](https://best-deals.pro/i/MgCPQuoc_uCrkqnbMC2amK--tXKISSw6BEKGevIEWgNNhKlKLX_ifZTVFCthqXhQ9PKfixXV7H0GLp8eo9ALSuiupZ0zVdu_-bWaoE-87icCseVMaS35h3o1.jpg)

![Filter King FKFD21X21-12 21x21x1 MERV 13 Air Filters, 12-Pack — 3](https://best-deals.pro/i/1Y3Kc9esL9BFI90vu9g8mRlt0i0kXh9rwjV0hWOZZrsaS6cKbP5NJbqU45kgvmZM7-GO4dVBgnCz7-MRkjlh7xpRfd7I_0jcJnZ6EnsiK6mPuj7DLu7C0iAD.jpg)

![Filter King FKFD21X21-12 21x21x1 MERV 13 Air Filters, 12-Pack — 4](https://best-deals.pro/i/Pd5xV4hlhPeF-X5OQ_kQDVCHbOvz4ljRdR85nKCQMEsBPgZdUT-PX86dRUcXQM4IqCVjvUtod8-USk5krc1cfVIiJlGjaqRYwNA4P-cq2Gv9G2OWpVUrhS1o.jpg)