Simply cut the high performance filter to the right amount and insert it into a Pit Mask, handmade mask, etc., and transform it into a high-performance mask. Kaken PFE test (0.1 μm ultra-fine particles) 99% non-woven fabric filter cuts out splash viruses and PM2.5, pollen and dust from 99% and 0.1 μm 99% filter. Efficient PFE testing for particulate filtration and filtration: conducted by Kaken Test by General Foundation). The sheet is 5.1 x 23.6 inches (13 x 60 cm), so please cut it to a size that is easy to use. If you use it for masks of medium size, it can be used for about 12 pieces, about 3 months supply); It can be washed once a day for a week, making it economical. A highly functional filter that cuts out intrusion viruses and PM2.5, pollen and dust by simply inserting it into a three-dimensional mask with a pocket or a handmade mask. When handling (cutting and packing) it will absorb fine dust etc. We will try our best to do it, but it is not possible to completely avoid the contact of fine dust and lint. Thank you for your understanding. Virtually no stretch. Due to the nature of the filter, there may be some pilling on it, but please use it without removing it. Please wash it gently with water. Do not use detergents or other similar products.