I switched to FilterBuy products last year and right away we noticed how much less dust was in the house. One of my filters is a custom size (5-7/8 x 15-18) and they fit every time.
The outside dimensions are a little bit larger both in the height and the width than the 14 and 8 inches as a result I had to squish the filter to get it into place. It just doesnt fall in easily