SafeHome Internal Frame MERV 8 Filter With Self-Sealing Edges Lets No Air Around Filter Safe Home TM Duo- 1625 has 2 filters surrounding a metal frame. 25 by 1 inch MERV 8 air purifier furnace filter. Note Check with your HVAC technician to verify that your system is able enough to handle the density of a MERV 8 filter before purchasing this or any other MERV 8 filter. Install this MERV 8 with Air Flow First Going through the White Media. Made in USA. Captures allergens, odors, and harmful chemicals. Fits standard 1 inch furnace panel slot or a return air grille with removable face for filter insert. Self-sealing edges all air goes through filter. Similar to hospital type filters. Duo replaces any 1 thick home air filter lasts up to 3 months. Install this MERV 8 with Air Flow First Going through the White Media. Safe Home Duo Filter Features Dimensions 16 x 25 x 1 Captures up to 95% of common household allergens Eliminates odors from pets, paint, cooking, and more Uses high density carbon and advanced compounds FormaldaSorb TM , a patented potassium permanganate product plus the activated carbon in the second layer of the filter trap gasses that can cause health issues. Highly effective and affordable. 2 stage air filter one MERV 8 rated polyester white allergen filter plus the activated carbon filter pad. Made in USA. How does the Duo work? The polyester outer layers remove pollen, mold spores, and other common allergens. The inner layer with FormaldaSorb TM and activated carbon traps a variety of odors and hazardous gasses, such as formaldehyde, ammonia, and others from cleaning chemicals, paint, particle board, and other household items. No other filters are as effective at removing dust mites, mold spores, pollen, odors, cleaning chemicals, ozone, paint fumes, and common gasses like formaldehyde which triggers asthma and allergies. Safe Home Duo One Inch Thick Filter Installation Determine direction of air flow through your furnace.