Air Duct 1.Specifictaion is as follows: 2.MT164-2007 3.dia300,dia 400,dia 500,dia 600,dia 800,dia 10001. air duct: Purpose: Fan machine could used it in coal mines, tunnel, underground for positive pressure ventilation.Air duct structure and dimension: structure:1-end ring 2-swinging ring installation line. 3-fling ring 4-reverseDimension: dia300,dia 400,dia 500,dia 600,dia 800,dia 1000(mm) ...