Aprilaire 4724 Seal Kit The contact between the inner housing and the door; the contact between the inner housing and outer housing Retrofit seal kit for both Old and new Style Aprilaire 2400 air cleaners. This kit contains 3 pieces of Polyester and 2 pieces of foam tape cut to fit the door, cabinet back and both ends of the media Frame This kit includes seals needed to seal contact between: filtering media and inner housing; contact between the inner housing and the door; contact between the inner housing and outer housing