Media for Model 2210 and 4200 (Merv 13). This is the replacement filter for the Model 4200 Aprilaire Air Cleaners. The filter can also be used in the Models 2200 and 2120, provided the upgrade kit, Part #1213 has been installed. The filter is the heart of the air cleaner and needs to be changed once a year or when your air cleaner control indicates it is time to change the filter. Use only genuine Aprilaire Selfseal #213 to ensure the best performance of your air cleaner.