Summary: I've been using a Holmes mini tower for at least a year and just purchased a large tower which uses two of these filters. I keep the smaller tower by my cat litter box - I have three cats in a studio apartment and dust is always a concern. The filters work great. I thought I would have to replace it more often than suggested in the manual, but the filter seems to be holding up really well despite the heavy usage - I keep the air purifier on 24/7.