This is the most powerful rooftop mounted whole house fan one can buy. QuietCool has one but it pulls much less air. The reason is they use a box for a rain hat that forces the air to go down before it can go up. This package comes with the 20 inch diameter shell you see in the picture and the rain hat you can see. Inside is a modern 1/2 HP EC motor that has infinitely variable speeds. The package includes a speed control dial. You can also get and an automatic control for opening a window when the air flows. This is important for you if you want to remotely start this fan from your car so your home is cool when you arrive. The AutoWin window control ensures your window cannot be opened by a burglar when closed or when opened.