""cakebox"" style filter with 4-inch thick media.
Upgrade to an Aprilaire Whole House Air Cleaner with this easy-to-install conversion kit. Aprilaire 4897 Conversion Frame for Competitive Media The frame can also used to upgrade an existing Space-Gard air cleaner and Aprilaire Models 220 and 2400 air cleaners. or 16 x 25 in.