These Air Innovations Humidifier Demineralization Filters are recommended for customers with hard water. Each filter will last up to 90 days depending upon usage and water quality.These powerful hard water filters help prevent white dust from forming in your humidifier by removing calcification and other impurities in the water. These demineralization filters are compatible with most Air Innovations Humidifier models including: MH-408, MH-504, MH-505, MH-509, MH-512, MH-513, MH-519, MH-519A, MH-526, MH-527, MH-602, MH-603, MH-701, MH-701B, MH-701BA, MH-701C, MH-702A, MH-703, MH-801, MH-801B, MH-901DA, MH-902, MH-903XL, MH-903A, MH-904, MH-906, MH-908 and more. Please Note: These hard water filters are not compatible with MH-901 or MH-901D humidifiers. Delivers clean, pure, healthy moistureBrand Name: Air Innovations Product Type: Humidifier Filter Number in Package: 2 pk Brand or Model Compatibility: Air Innovations Depth: 2-3/4 in. Packaging Type: Boxed Antimicrobial: Yes Width: 4-1/2 in. Height: 4-1/4 in. Air Innovations Humidifier Models: MH-408, MH-505, MH-509, MH-512, MH-513, MH-519, MH-519A, MH-602, MH-603, MH-701, MH-701B, MH-701C, MH-702A, MH-801, MH-801B, MH-903XL, MH-903A, MH-904