Review on High Performance Motorcraft FA-1908 Air Filter by Jordan Doyle

I've read reviews that this filter (and others) is too long to fit in the airbox. I assumed it was all user error for not setting the filter properly. I was wrong. This is actually the correct part number from my Ford owner's manual. However, the filter medium is definitely different. Also, it was about 1/4 inch longer. Regardless, I think you should get it working. I thought about it for a few minutes and noticed that the creases on the original piece weren't distributed neatly, like they were dented. If you look inside the filter you will see that there is a system of plastic ribs that are not connected top to bottom. There is a distance of about 1 inch from the end of the ribs to the hole. This will allow you to work with the creases in a twist and pinch motion in that area. I was able to shrink the filter fairly easily to fit afterwards. The filter seems to breathe easier, which I like about my 2018 Focus RS. I'm not too worried about the other filter media, but the original was yellow cardboard and the new one was white paper/pulp. I plan to use genuine filters as K&N before the warranty expires. I have 2 of these and they fit my old 2013 ST airbox perfectly, so I'm pretty sure they fit my RS airbox perfectly. If you want a filter that really fits perfectly, a washable K&N filter will definitely do (and it doesn't have that notch so you can just flip it over if one side gets dirtier than the other).