Krisvie Activated Carbon Dustproof Dust Mask Filtration Exhaust Gas PM2.5 for Running Cycling Outdoor Activities UNIQUE DESIGN: Unique ventilation design, a plurality of holes, excellent permeability, Exhale ,the valve is opened without resistance ,double air breathing valve, air resistance is smaller ,smooth breathing The mask can be washed when they get dirty,The mask filters can be replaced by yourself,simple,frugal and fun SUIT FOR MOST PEOPLE: Size can be adjusted to meet the most head type.According to the person face design, keep out the bridge of the nose the following part, have the nose clip fixed, to prevent the slide MULTI-USAGE:Dust mask is perfect for cycling, motorcycle, woodworking,running and other outdoor activities 100% MONEY BACK GUARANTEE & 100% QC: 100% quality checking, We devote ourselves to provide customer service and bring the best shopping experience to every customer. If you are have any question, pls feel free to contact us and we will help you solve the question