Genuine Aprilaire 501 high efficiency replacement filter. Used in the model 5000 air cleaner. The Aprilaire 5000 is rated #1 by the leading product magazine for 3 years running.
The Stock No. 501 filter is 27¼" long and 6¼" wide with 32 fan-fold pleats. The filter requires assembly with 5 plasitic pleat spacers (not included).
Replacement is suggested once a year or after one heating and one cooling season. Holding the filter up to light will show the amount of dirt. Only the intake side should be dirty, the side of the filter that the air exits from should remain dust free.
Aprilaire was formally the Spacegard. Aprilaire is a brand name of Research Products. The genuine Aprilaire 501 is made in the USA.
Each filter is individually boxed as shown in our photos.