I have been buying this filter for a while now. I do replace it every two months as my asthma, allergies, health issues require me to do so. This is the highest number filter I can find so far as I have an uncommon filter size 16 x 24 x 1 apparently. I do like the filter. Can't say anything negative about it. I do wish that I could order it on-line and have been able to figure out how yet. Great Filter. I highly recommend it to anyone with allergies, asthma, and health issues.