I recently used this mask on a cross-country trip. The bridge of my nose wasn't sore as sometimes happens and I had no difficulty breathing. Under the right conditions, longer use of this mask can be very helpful. Women with large bone structures in their faces will take a medium. Average to small men should take a small as well.
Available sizes are small, medium, and large.
There is no extra-small. There is only one filter size. The biggest drawback to the North Safety masks is that the silicon stinks when you first get it. It will fade over time. When the mask is a year or more old you shouldn't be able to smell it at all.