This Air-Care EF1820 is an 18 in. x 20 in. x 1 in. flexible permanent washable electrostatic air filter designed for HVAC and furnace systems that require non-standard or unique filter sizes. Featuring a flexible frame design, it yields a versatile fit for irregular setups without the rigid metal constraints of traditional options. The electrostatic fiber design generates a natural static charge as air flows through it to attract and trap airborne contaminants such as dust, pollen, mold spores, pet dander, and allergens down to 1 micron, functioning up to 10 times more efficiently than standard disposable filters. This MERV 8 rated filter is a reusable and eco-friendly alternative to disposable models, requiring cleaning only every 1 to 3 months via simple water washing. This specific unit is in fair used condition and remains functional for continuous air purification support