Developed by a filter specialist manufacturer Enhances mask performance Patented nanofiber sheet Made in Japan - Product Name: Yamashin Filter Sheet - Quantity: 30 sheets - Features: 99% cut of fine particles - Size: 140mm x 85mm - Price: 1,078 yen (tax included) Can be hand-washed and reused, making it economical. Simply insert it inside your mask for use.