As a respirator, our KN95 forms a tight seal around the nose and mouth and is designed to block even small particles. Fitting the mask correctly is crucial to make it effective. Guidance of fitting the mask correctly is shown on the package.
Material: Non-Woven, 4 layers
Non-woven fabric (first layer) + melt-blown fabric (second layer) + Hot air cotton (third layer) + Non-woven fabric (fourth layer)
I bought these on Neodian's page for elderly persons (male) and also used them for myself. They come in a resealable bag so this prevents contamination, and they do not need to be thrown away after a single-use. We used it for up to 12 hours, putting it on and off when necessary. Great price (cheapest I've seen?) but at the proper quality needed.