These filters aren't the measurement indicated. Received ours and put one in the furnace and it flip flopped from side to side and top to bottom. Our furnace company said that this will cause the furnace to work harder putting undo strain on it. We returned the filters.
Have been using this product for 2 plus years. Upon upgrading to the Merv 13 filtration, I noticed some dustballs collecting on the filters after first couple of filter changes. Now, no dustballs. These filters use "nominal" sizing. I had to add shims to filter box in order to prevent air bypass. I use the 4" deep filters and change every 4 months. I'm very satisfied with performance of these filters and will continue to use.