I bought this for biking to work, but found it completely unsuitable for this use until I modified it with scissors.  The tiny pinholes for the mouth are completely inadequate if you are breathing hard from exercise, as is the small nose hole - I felt as though I was suffocating and had to take it off!  To make matters worse, I wear glasses, and my breath, having nowhere else to go, was forced out through the top, fogging and frosting my glasses to the point of blindness.

All these problems were solved after I took a pair of scissors and cut out a large hole for my mouth and a smaller one for my nose.  Now I can breath, the fogging is cured, and the mask is suitable for biking, keeping my face warm.  I like the fact that the mask attaches easily, with velcro in the back.  I recommend fastening the straps high, above the hairline, rather than around the neck, to avoid the mask riding down your face as you bike.