This filter (30x36") was assembled from two smaller filters, one of which was cut. the resulting joint was sealed poorly, resulting in an entire "loose" edge of filter element material along the short axis. This results in high-velocity air-flow along this seam and allows unfiltered air to by-pass the filter element.
Would be nice to be able to talk with someone about sizes. As in my case I ordered one size but under it in small print was another size. I haven't used yet so I don't even know if they will work.
Do not correctly fit the canister (Miracle MAte/Tristar) I have wiithout some "McGyvering" adjustment. It lets dust and particles out into the canister