re fit: I agree, they are less than perfect. They are round and don't seal very well, that said, in my case and probably most of you, I like the change in flow and am not concerned with allergies. I really don't see how they would filter anything myself, but they are close to what I was trying to build. I wish they went in a little farther and they could be shaped more like your nose for sure but compared to the clips I make, these are elegant looking. My clips do serve a different purpose but for some day time protection without looking like a dork, these are worth a try for the price. They are also re-usable, cleanable. There is no paper filter, it is a one piece silicon type material that I can't see ever going bad. I may cut up one pair to stuff them in farther. I also cut up one pair to open the hole that you breathe through just a little as it was too restrictive for sleep, yet even modified, didn't help with my sleep. My problem (well ONE of my problems) is that my ITs change during sleep and dry out and swell up a bit so that is tough to fix.