the Aeroboy as described very easy to retrofit ... and by desTeleskopabluftrohr, for many walls and structures to use. Quick installed as a good German instructions enclosed. Furthermore, and more ... Screws / dowels. And he is close ... allso As for the cold, which remains out side now. He looks at the wall and correct quality of .... What betrieft the price I have to pay wages to the hardware store for a simple rattle blind without backflow flap 13.5 .... I've thrown away after the first gust of wind and bought the Aeroboy ....