Designed to be used with the 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. Key Features 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 Filter should be replaced after 12 hours of use Pack of 10 filter inserts