Key Features: Designed to be used with our Element & 3D reusable face coverings,This 5-layer filter adds additional protection to our face covering,Non-woven inner and outer layers prevent larger dust particles from passing through and provide ,structure and support for the finer filtration layers,Polypropylene melt-blown layers prevent smaller particles from passing through the filter, down to a size of approximately 3 microns,The activated carbon is a highly microporous filtration layer which absorbs smaller gaseous impurities via chemical adsorption,Pack of 10 filter inserts.