The aerodynamic pressure drop is low and the slats are mounted so that they do not allow raindrops to enter. Grilles are constructed of galvanized metal sheets with (-AL) or without aluminum frame. Insect net installation is possible on customer's request (+IN). They are installed directly onto the air duct without an aluminum frame, or onto the building structure with an aluminum frame. The air flow rate of single ventilation grille can be from 100m3/h up to over 1000m3/h (27l/s – over 278l/s).