Black Ops Carbon filters feature virgin activated Australian RC-4/12 granular carbon. The activated carbon absorbs and traps pollutant molecules within the carbon removing contaminants, odors and impurities from the air. Machine packing allows for more carbon and less movement. The open air mesh design maximizes airflow. These filters are light-weight and have powder coated aluminum tops & bases. Black Ops filters have a built in flange and 2 pre-filters are included. They are sized to meet all of your ventilation and air purification needs. 2 year life expectancy.