These pre filters do not compare to the Honeywell brand that originally came with my Honeywell air purifier. They are at least half as thick and thus not rigid enough to stay flat against the inside filters. Without proper coverage of the inside filters, more dirt will get in. Also, I had to hold them in front of a wall heater to get the fold shape out of them before installing. I will only buy Honeywell pre filters from now on.