Honeywell Universal Air Cleaner Prefilter (2 uses) - 8 Pack
Fits Honeywell model 17400.
It takes less than five minutes to change the pre-filter.
This filter is larger (taller) than it needs to be for your machine. You simply trim the filter (and it's got pre-made perforations) to the height of your machine.
Replacing the pre-filter at least every three months is recommended.