Product review (5 stars): Very Impressed!
These disposable filters are wonderful. Living in the country with gravel roads and a gravel driveway my box fans get filthy within a month. The longest the filters  last for us is two weeks but for those who live in town, the filters would last so much longer. They aren't inexpensive but so worth it. Taking apart a box fan and cleaning it is time consuming and a chore that I never did often enough. No longer am I embarrassed with filthy fans. I've also noticed noticed my dust allergy is so much better. Whoever came up with this product, I say thank you multiple times!