Bought these for my 2007 GMC Sierra Classic. You install them by sliding them on to your factory mirror and then pulling the upper lip of the towing mirror over the top of the factory mirror. This makes for a very tight fit and seems to put a fair amount of stress on the plastic. Also, the adjustment bar that's included with the mirrors (that fits inside to keep them tight) is only covered with a thin layer of felt paper. When I removed the mirrors, I had some marks in the plastic of my factory mirrors. I would not recommend using these on any mirror that's painted or has the chrome cover, as it would most likely scratch very easily. In the owner's manual, it recommends waxing your factory mirrors but this probably won't be enough to protect them.Using the mirrors, they worked great. The don't vibrate or whistle in the wind. They integrate with with lines of the truck well and look like a factory option. The glass tilts in all directions and once you set it to the...