Abilities
*usable in return and offloading for all places.
*  Instal location on the wall or false wall
*usable in ventilation control in a zoon
* very low in pressure  decreasing  for blowing and offloading air (ventilation)
*Able to instal kinds of dampers for ventilation control
*Able to ventilate in 1   2   3   4   - side and rotating
* Long length  throwing
* ventilation in manner of string  
* Low voice