19 3/4x21 1/2x1 Aerostar Air Filter

The 19 3/4 x 21 1/2 x 1 Aerostar fits a return that nominally would be called a 20x22x1 but actually measures 19 3/4" x 21 1/2" x 1". Odd-sized returns like this appear in custom HVAC installations and certain regional construction markets where the original installer didn't size to a standard nominal opening. MERV 8 covers standard residential dust and pollen filtration. MERV 11 handles pet households and most common allergens. MERV 13 captures fine particulates including smoke, bacteria, and virus carriers - the grade for households with respiratory issues or in wildfire-affected regions. Pleated synthetic media with an electrostatic charge built into the fibers does the actual filtration work. The pleats give you substantially more surface area than a flat fiberglass filter at the same nominal size, extending the service life to a 60-to-90-day window in typical residential conditions. The electrostatic charge catches sub-micron particles where the physical weave alone reaches its limits. Manufactured in the USA by Con-Air Industries, Orlando, Florida. Cardboard frame, reinforced to maintain shape under blower suction. Odd-size filters benefit most from dimensional precision because an off-spec filter leaves gaps where unfiltered air bypasses the media entirely.