Ship from USA- Package: 21pcs PM2.5 Activated Carbon Replaceable Anti Haze Filter /bag. Five Layer Protection: 1st layer of spunbond cloth filters micron-level dust. 2nd layer filters industrial pollutants, automobile exhaust, passive pollen allergens. 3rd layer of active carbon cloth filters micron-level dust. 4th layer offers filter density for smaller material. 5th layer of spunbond cloth filters out all kinds of harmful substances. Material: meltblown cloth, non woven, active carbon cloth Fiber diameter of meltblown cloth effectively filtering PM2.5, pollutants and droplets. Filters Size Adult: 12 x 8 cm/ 4.7 x 3.1 inches. Filter inserts cannot be cleaned and should be replaced weekly. Please feel free to contact us by email if you have any questions, we will be be happy to assist.