It's a breathing mask that includes a one-way valve to make it easier to exhale heat, water vapor, and carbon dioxide.

• Choose Oxford Mask Pro KN95 With Breathing Valve - Extra Large (175*220 mm)
  

Composition and Accessory:

• Mask x 1 pc
• User Manual x 1 pc
• Filter x 2 pcs
• Threaded Buckle x 2 pcs
• Inner Nose Clip x 1 pc
• Breathing Valve x 1 Set 

5 Ply Filter:

• Oxford Pro applies a unique 5 layers filter system, help you breath more healthy air.
• This multi layered filter system makes the mask perform better and lasts longer than other masks on the market.
• Effectively protect you from non-oily  particles like pollen, dust PM 2.5 etc.
• There are 2 replaceable filters to supply in the mask set and filter can be bought separately as well.

Breathing Valve:

• The breathing valve can make the wearer's breathing resistance lower, will ease discharge of hot air from the mask, and the wearing experience will be improved, making you feel more comfortable.

Product Features:

• Mask are comfortable, breathable, and not easily deformed.
• Elastic Edges to fully match different faces.
• Fasten button t adjust mask fully fit face shape.
• Replaceable 5 ply filter: Non-woven, melt blown, activated carbon
• 3D shape, washable, Reusable.