The best
After trying a lot of different masks I find this one to be the best overall and I believe it is the best filtration available when I insert the 2.5 filters.  The little adjusters on the ear lanyards tend to slip after a little time wearing but once I get them to the best place I tie a knot next to the adjuster so it can't move.  They are the most comfortable masks I have tried and make a good seal with the metal nose band.
Rating: 5 stars