Original title: Do you really understand the structure of KN95 mask? Do you really know the structure of KN95 mask? Medical masks and protective masks are non-woven materials,KN95 Mask with Fast Shipping, composed of directional or random fibers, generally multi-layer structure,Antivirus Disposable Mask with CE Certificate, usually referred to as SMS structure (2 layers of S layer and 1 layer...