Swine Flu N95 Mask with one way valve box of 10This is an N95 mask with one-way valve. A one-way valve allows you to exhale with air going outside the mask rather than staying inside your mask; it makes breathing easier. They are more expensive than regular N95 masks. This is not a 3M brand mask. Order item 11390. Box of 10. ***NOTE: Our inventory has an expiration date on the box of November 2013. Therefore, we have reduced the price to clear out.