21x21x4 Air Filter
Efficiency	APR 1950	APR 1950	APR 1550	APR 1550	APR 650	APR 650	Carbon	Carbon
Equivalent	Merv 13	Merv 13	Merv 11	Merv 11	Merv 8	Merv 8	N/A	N/A
Performance	Best	Best	Better	Better	Good	Good	N/A	N/A
Actual Size	20.5x20.5x3.75	Actual Size	20.5x20.5x3.75	Actual Size	20.5x20.5x3.75	Actual Size	20.5x20.5x3.75	Actual Size
Brand	Accumulair	Accumulair	Accumulair	Accumulair	Accumulair	Accumulair	Accumulair	Accumulair
Item #	FD21X21X4	FD21X21X4A	FA21X21X4	FA21X21X4A	FB21X21X4	FB21X21X4A	FO21X21X4	FO21X21X4A
Purchase	$22.43 Min Qty: 2 Order Options	$22.43 Min Qty: 2 Order Options	$27.71 Min Qty: 2 Order Options	$27.71 Min Qty: 2 Order Options	$21.11 Min Qty: 2 Order Options	$21.11 Min Qty: 2 Order Options	$35.63 Min Qty: 2 Order Options	$35.63 Min Qty: 2 Order Options
Product Page	More Info »	More Info »	More Info »	More Info »	More Info »	More Info »	More Info »	More Info »

21x21x4

Air Filter

Efficiency: APR 1950

Equivalent: Merv 13

Performance: Best

Actual Size: 20.5x20.5x3.75

Brand: Accumulair

Item # FD21X21X4

$22.43

Min Qty: 2

Order Options

Efficiency: APR 1950

Equivalent: Merv 13

Performance: Best

Actual Size: Actual Size

Brand: Accumulair

Item # FD21X21X4A

$22.43

Min Qty: 2

Order Options

Efficiency: APR 1550

Equivalent: Merv 11

Performance: Better

Actual Size: 20.5x20.5x3.75

Brand: Accumulair

Item # FA21X21X4

$27.71

Min Qty: 2

Order Options

Efficiency: APR 1550

Equivalent: Merv 11

Performance: Better

Actual Size: Actual Size

Brand: Accumulair

Item # FA21X21X4A

$27.71

Min Qty: 2

Order Options

Efficiency: APR 650

Equivalent: Merv 8

Performance: Good

Actual Size: 20.5x20.5x3.75

Brand: Accumulair

Item # FB21X21X4

$21.11

Min Qty: 2

Order Options

Efficiency: APR 650

Equivalent: Merv 8

Performance: Good

Actual Size: Actual Size

Brand: Accumulair

Item # FB21X21X4A

$21.11

Min Qty: 2

Order Options

Efficiency: Carbon

Equivalent: N/A

Performance: N/A

Actual Size: 20.5x20.5x3.75

Brand: Accumulair

Item # FO21X21X4

$35.63

Min Qty: 2

Order Options

Efficiency: Carbon

Equivalent: N/A

Performance: N/A

Actual Size: Actual Size

Brand: Accumulair

Item # FO21X21X4A

$35.63

Min Qty: 2

Order Options

The manufacturer has discontinued the MERV 6 / APR 450 filters from their line up, our suggested replacement is the MERV 8 / APR 650 Gold filter, you may see the Emerald MERV 6 / APR 450 still on the website, we are actively removing that MERV/APR

** The typical ship time for orders is now around 15 to 20 business days **

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21x21x4

Air Filter

Efficiency

APR 1950

APR 1950

APR 1550

APR 1550

APR 650

APR 650

Carbon

Carbon

Equivalent

Merv 13

Merv 13

Merv 11

Merv 11

Merv 8

Merv 8

N/A

N/A

Performance

Best

Best

Better

Better

Good

Good

N/A

N/A

Actual Size

20.5x20.5x3.75

Actual Size

20.5x20.5x3.75

Actual Size

20.5x20.5x3.75

Actual Size

20.5x20.5x3.75

Actual Size

Brand

Accumulair

Accumulair

Accumulair

Accumulair

Accumulair

Accumulair

Accumulair

Accumulair

Item #

FD21X21X4

FD21X21X4A

FA21X21X4

FA21X21X4A

FB21X21X4

FB21X21X4A

FO21X21X4

FO21X21X4A

Purchase

$22.43

Min Qty: 2

$22.43

Min Qty: 2

$27.71

Min Qty: 2

$27.71

Min Qty: 2

$21.11

Min Qty: 2

$21.11

Min Qty: 2

$35.63

Min Qty: 2

$35.63

Min Qty: 2

Product Page

21x21x4

Air Filter

Efficiency: APR 1950

Equivalent: Merv 13

Performance: Best