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Part number20 x 25 x 4 in actual size
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Nominal size
20 x 25 x 4 in
Actual size
19.75 x 24.25 x 3.625 in
Depth class
4 in (media cabinet)
Order by
nominal size (20 x 25 x 4 in)
Typically installed on
media cabinets for the Aprilaire 1210/2210/4200 and Honeywell F100 20x25

The true measured dimensions of a 20 x 25 x 4 in filter and how to order it.

A 20 x 25 x 4 in filter actually measures 19.75 x 24.25 x 3.625 in. Buy it by the nominal size 20 x 25 x 4 in; a filter cut to the exact nominal number would not slide into the slot.
Fitment notes

The nominal size 20 x 25 x 4 in is the name on the frame; the actual size is 19.75 x 24.25 x 3.625 in. On a flat filter each face runs about half an inch under nominal and a one-inch filter is really three quarters of an inch thick.

The wide four-inch media filter. It seats in an Aprilaire 1210/2210 or Honeywell F100 20x25 cabinet and takes the Aprilaire 210 or 213 media. It is not interchangeable with the six-inch Aprilaire 2200 filter despite both being 20 by 25.

What to buy

Find your model

Read the number stamped on the humidifier cabinet or printed on the old pad, then match it below. Confirm the frame size before buying a generic.

Related

Sources: AprilAire 210 MERV 11 air filter product page ยท Aprilaire 213-APR MERV 13 media for 1210/2210/3210/4200 (SupplyHouse)