KN95 Face Mask Anti Dust Bacterial N95 Mask 4-Layer PM2.5 Dustproof Protective Filtration 95% KN95Specifications: Validity: three years Compound standard: GB2626 2006 Filtration efficiency: non oily particulate matter filtration rate> = 95% Product storage: storage temperature 20 38C, less than or equal to 80% RH in spring, need to be stored and well ventilated, protected from light, dry environment, and away from pollution sources How to use: Wash your hands first, then tie a rope around your neck, pull the upper rope to the middle of your head,