LingAo Activated Carbon Dustproof Dust Mask - with Extra Filter Cotton Sheet and Valves for Exhaust Gas, Pollen Allergy, PM2.5, Running, Cycling, Outdoor Activities UNIQUE DESIGN:: With unique ventilation design, a plurality of holes, excellent permeability, exhale, the valve of work out mask is opened without resistance, double air breathing valve, air resistance is smaller, smooth breathing. CONVENIENT REPLACE: Easy replaceable filters,the product includes one activated carbon masks, two valves and filter cotton, you can replace by yourself .The mesh cover can be washed to keep clean. MULTIPLE FUNCTION:Separation of 98% of the dust, chemicals, smoke and particles, It can be used for dust, anti-vehicle exhaust, anti-pollen allergy, PM2.5, for cycling, hiking, skiing and other outdoor activitie SUIT FOR MOST PEOPLE: Size can be adjusted to meet the most head type. WARRANTY : we have 100% faith on quality and provide 30 days money back warranty