1 FILTER, ACTUAL SIZE IS 1/2″ LESS THAN STATED DIMENSIONS LIKE ALL STANDARD FILTERS! Meets manufacturer specifications for low initial resistance to air flow. A combination of woven and unique high loft polypropylene enclosed in a nominal 1″ or 2″ metal frame. No modifications needed to the furnace No electrical connections needed, air flow charges filter Helps remove tobacco smoke Improves the air for allergy sufferers Cuts down on dusting Eliminates many odors Filter should outlast your furnace These filters are recommended to be washed out every 4 to 6 weeks. Remove your filter and use a vacuum to remove dust. Then use water to rinse the opposite direction of the airflow that you had the filter installed. A light cleaner such as dish or laundry soap can be used to remove cigarette smoke or other contaminants. Rinse the filter out very well, allow it to dry and put it back in your unit. Do not leave your filter out in sunlight or high heat situations for any long period of time. The 1″ has 4 layers of lifetime expanded aluminum and 2 layers of electrostatic filter media for a total 6 STAGE FILTRATION!. The 2″ has 5 layers of lifetime expanded aluminum and 2 layers of electrostatic media for a 7 STAGE FILTRATION! Researchers now agree there may be a greater number of irritating pollutants indoors than outdoors. The result is recirculated stale air contaminated by dust, fibers, fumes, cleaning chemicals and solvents, bacteria and mold. These invisible particles are causing you the discomfort and irritation of itchy, watery eyes, sneezing, wheezing and other adverse reactions. Electrostatic air filters use air and static electricity to capture airborne particles. There are no electrical connections needed. The air flow from your home ventilation system moves over the filter media, enhancing its charge field. As airborne particles approach the charge field, they are drawn into the media and held until the filter is cleaned.