Activated Carbon Dustproof/Dust Mask – Filter Cotton Sheet and Valves for Exhaust Gas, Pollen Allergy, PM2.5, 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 EASY TO REPLACE: The mask can be washed when they get dirty.And you can replace them with another new activated carbon masks, valves and filter cotton by yourself.(Not included.) […]