Accumulair MERV 13#201 Replacement Media for Aprilaire Models 2200/2250 Accumulair #201 Replacement Media for Aprilaire Space Guard 2200/2250 Reaches 99% efficiency on particles 3 microns or larger Improves efficiency and increases longevity of HVAC systems when properly used and maintained High efficiency filter media collects small dust particles before they can collect on your coils This is an aftermarket filter.