The MaskiT World Flags Reusable 3 Layer Masks are designed to prevent transmission of airborne particles up to 2.5 microns. The outer cotton layer is reusable and machine washable. Each mask comes with 3 PM2.5 disposable filters that slide between the cotton layers. Additionally, each mask comes with adjustable earloops to help create a comfortable fit.  These masks are not considered medical grade. IMPORTANT: This mask is intended to be worn as a fashion accessory only this mask will not provide protection against bacteria or viruses.