PadMatch

PadMatch / Every humidifier water panel and furnace filter size

Part numberAprilAire 45 vs AprilAire 35
no
AprilAire 45
9.875 in W x 12.875 in H x 1.75 in D (nominal 10 x 13 x 2)
AprilAire 35
10 in W x 13 in H x 1.75 in D
AprilAire 45 fits
AprilAire 400, 400A, 400M
AprilAire 35 fits
AprilAire 350, 360, 560, 560A, 568, 600, 600A, 600M, 700, 700A, 700M, 760, 760A, 768

Whether the AprilAire 45 and AprilAire 35 humidifier pads interchange.

Not interchangeable. The AprilAire 45 and AprilAire 35 fit different humidifiers.
Fitment notes

These are both Aprilaire but are not related. The 45 is a paper wick for the drainless 400 unit; the 35 is a coated mesh panel for the 600 and 700 units. Neither fits the other's humidifier.

The 400 series is the odd one out in the Aprilaire range. If your unit is a 400 or 400M, only the 45 wick fits, and it installs in either orientation with no paint dot.

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 Water Panel 45 product page · AprilAire Water Panel Guide · AprilAire Water Panel 35 product page