pretty good basic filter
I got these filters mainly to use with homemade cloth masks and ordered a "large" and it seems to be just about enough to cover my nose and mouth without concerns about slipping down. The filter is not very thick, but it is tightly woven. As an addition to a mask that is already 2-3 layers, I found it to be satisfactory without making it too hard to breath through. The only down side to these was that they have slits across the bottom and top to make them fit your face more accurate by angling. I would have preferred to cut them myself because they are cut a bit longer than I need and that increases the likelihood of gaps. However, with a good pocket, I think they should work very well.
Rating: 4 stars