Maskº has been developed with healthcare professionals for comfort over long-term use, and utilizes a replaceable single-use filtration membrane for maximum efficacy. Each Maskº is made of washable fabric and contains a pocket in which a single-use filtration membrane can be easily inserted.The filter element provided has been independently tested by Nelson Labs to provide higher than 95% Bacterial Filtration Efficiency (BFE ≥ 95% ). Ships with 10 filter inserts, each good for 8 hours of use.