if like me you have a ford with a heated windscreen this is vital if you want the sat nav to work, the fliaments in the screen reflect the gps signal so the sat nav does not know where it is, i plugged this in and within a minute the unit had a strong and clear signal, a well made item and great value for money , oh i almost forgot , put a little bit of cloth under the antenna stops it scratching the paintwork
update update !!!!!!!!!!!!!!!!
have used this on several occasions now and has performed faultlessly, it had improved the performance of our sat nav 100 o/o now if only i could figure out how to update the maps on it i`d be well happy