Indoor Air Quality matters. That's why you trust Aprilaire® to keep your home environment safe for you and your family. This is a genuine Aprilaire® 261 Air Filter Replacement. It's proven to prevent particles between 3 and 10 mic from passing through your home's heating and cooling system. That includes dust, pollen and mold spores, which can irritate allergies and worsen asthma symptoms. Annual air filter replacements are a great way to keep your home and family protected. Aprilaire®, Trusted Solutions for a Healthy Home.