The Walgreens 809997 Compatible Humidifier Filter features a honeycomb filtration to trap mineral pollutants found in water and help prevent them from entering your home and fits Wallgreen models 6610 and 809997. The 80997 filter measures approximately 6" x 9" x 1 3/8". For optimum performance, replace filter at the beginning of each season or every 2 months depending on use.