-Replaceable PM2.5 Filter
-Provides 5 extra layers of filtering protection in addition to cotton mask
-Not washable or resuable
-Recommended to use with the cotton face mask 
-Keep a layer of face mask fabric between filter and your mouth (Use with face masks that have an open slit in mask that allows filter to be slid inside)
-Recommended lifespan of 3-4 days (Replace every 3-4 days)
-Packaged in pack of 10 pcs