I started doing research on roof ventilation about two months ago. I was not pleased with the appearance of the ridge roof vents or the spinning roof turbines (they always seem to require lubrication). This is why I chose the Aura Ventilators. I purchased 2 AV-18's.They were very easy to install. I used the side of the shipping box to make a template. After installation I immediately notice a two degree reduction in temperature inside our home, especially the great room. The Aura ventilators cannot be seen from street level when installed on the back of the house using a 2 inch collar. Water leakage has not presented itself as a problem on a 6/12 pitch roof. In fact I will probably install a pair on my rental home, also my mother-in-laws home.