Hey Don, there are two reasons that I went with a professional detailer with experience with Ceramic Pro. First, the key to success with whatever you do is an extremely fastidious prepping of the vehicle's paint surface. Washing, claying, buffing imperfections if needed, getting into all the nooks and crannies of the body design (my guy included the door plates, for example, for cleaning and application) and as much as I adore my new car, I don't have the patience to do all this. Maybe you do. And secondly, as Nineball mentions, professional detailers have the training and equipment to handle industrial strength versions of the same stuff you can get online. They also work in well-lit, well-ventilated, and temperature controlled environments. My car got four layers of the nano sealant, and then a top coat of a variation that requires an annual refresh (which I figure is about what you would be able to buy independently). My detailer had access to other variations of Ceramic Pro for doing the exhaust pipe tips inside and out, and for the wheels, which they removed, marked for placement and treated inside and out along with the calipers. I even went for the glass treatment. The process took two or three days and cost about $2,300.