The weather protection grid, System 781D-RC3, from MLL Hamburg, is a burglar-resistant, RC3-tested ventilation grid made of aluminium with a free ventilation cross section of 36%. You can gain security and still not have to do without fresh air or ventilation in a room or building. Thanks to the reinforced MLL slats, penetration into the inside is prevented to the greatest extent possible. The system 781D-RC3 is equipped with an elliptical slat in a reinforced Frame 702.