I am very surprised of the efficiency given the price. This is a very good surprise. It is very easy to put on and very comfortable to wear, better than its more expensive competitor! By cons, it has no active carbon filter, and saw with time (2 months) an expiration valve closes when evil inspires and then lets the pollution (you feel the suddenly very quickly!), which made me change range ... It still remains a good product for occasional use. Personally I'm in town on a scooter and in tunnels and traffic jams almost every day so I went to the game over.