I used UNI filters for the first time last summer. I like the ease of cleaning them. The one thing I noticed when removeing the filter. Is the inner filter was always caved in as if it was being sucked into the ariboot. Is that commom with UNI. It just didn't seem right any guesses as to why mine did this. At first I thought I over oiled it. Nope that wasn't it. I didn't like it so went back to Twin Air.