There seems to be a large variety in appearance of the filters available, some have concertinaed filter blades, some are straight. These look to be quite a small filter as well so filter material area and the properties of the filter material itself could have an impact on both the flow of oil and the size of particles filtered out. For the extra few pounds I paid for a genuine Ford item it seems worth it for the peace of mind that the filter properties are correct. Much cheaper than a replacement engine...