Aprilaire Humidifier Pad (2 pack)
The Aprilaire humidifier pad absorbs water from a tray while a fan blows air through it. The air picks up moisture and carries it throughout the room. This filter should be replaced 2 times a season. Fits Aprilaire models 400, 400A, 400M and other brands with a 10″x12-3/4″x1-3/4″ pad.