Non woven poly-propylene filters offer the protection within a mask that actually makes the difference. The non-woven part means that the fibers are laid down in a random pattern making them a better filtration. This fabric is estimated to filter .05 micron (N95 filters .03 microns).
This product will also hold onto wet particulates from sneezes and coughs until the cotton fabric of your mask absorbs and holds it.
These are offered in a pack of 5 (they will vary in color). Each is 2 layers and serged together for ease of use and cleaning.
These need to be hand washed and line dried as they will melt under heat. They can be autoclaved for 6-9 months.