Square 28x28x1 returns appear on larger residential systems and some compact commercial air handlers. This Aerostar measures 28" x 28" x 1" actual - one of the rare sizes where nominal and actual specifications match. MERV 8 covers baseline residential filtration for dust, lint, and pollen. MERV 11 handles pet households and most common allergen concerns. MERV 13 captures fine particulates including smoke, bacteria, and virus-carrying droplets - 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 work. The pleats give you substantially more surface area than a flat fiberglass filter at the same nominal size, which extends the service life to 60 to 90 days under 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. Larger filters experience proportionally more total suction force across the filter face, which is what makes reinforced frame construction matter more at this size than on smaller filters. Frame collapse on a 28x28 lets in substantial bypass air - this filter holds shape.
