Each är Nanofilter contains three layers of nanotechnology, which has been tested by Nelson Labs. The nanofibers within the filter, whose average thickness ranges between 100 nm - 500 nm, are 1,000 times thinner than a human hair! While these fibers act as a filter, the porous weave means easy, comfortable breathing. These filters are replaceable, giving you the freedom of everyday use. Each mask includes 1 replaceable är Nanofilter for free. The nanofibers within the filter, whose average thickness ranges between 100 nm - 500 nm, are 1,000 times thinner than a human hair! While these fibers act as a filter, the porous weave means easy, comfortable breathing. They give style to the most cutting-edge of technologies. Their masks are designed and produced in state-of-the-art facilities within the EU so you can use a high quality mask and still feel stylish wearing it.