Haven't had the windows down whilst driving yet (too bloody cold) but if they're like my others they should be fine, obviously the more the window is open the less effective they become. Very easy to fit, just a few minutes each side, although a little tricky at the mirror end. Citroen quoted me £45 which I thought was plenty dear enough for a bit of plastic. These look nice and blend in a treat I feel without sticking out too far.