Airtrim is a facemask that will help you breathe better in cold dry air conditions. It is a heat/moisture exchanger which recovers the heat and moisture from exhaled air. The filter heats the air you breathe in, protecting your air passages from the cold. Includes one each of racing filters 1, 2, and 3. The racing filters allow for more airflow than the Sport/Asthma filter for higher intensity activity. 1 is the least airflow and 3 is the most.