Thought I was ordering a 4 inch filter but was actually 3 1/2 . The Honeywell filter it replaced was a full 4 inches so I guess you get what you pay for.
I don't like them at all. The size of the filter is not exactly 20" X 20" X 4" and I had to shim the filter up with cardboard to get the fit needed. If you don't shim it it will make a clicking noise when the unit comes on and I'm sure dust is getting around the filter.