Felt and foam filters are ideal. I liked the little pull tab that makes it easier to take it out of the car when the time comes. The previous one had no tab. I measured the filter and to be honest I was confused. I didn't have any of the measurements mentioned, so I felt like I measured wrong (I didn't measure the rib or whatever at the top. I should have measured that part as well). I need a filter and will not pay Shark more than $30 for their filter. I read reviews and felt confident seeing people posting machines similar to mine and saying they fit. It actually fits in the car, but you can't close the case completely.