It's a silicone based wax, just as BenTheMan said. It's perfectly safe for windshields, headlamps and the mirrors on the outside of your vehicle. Over time, just like all glass, windshields become pitted and scratched. Rain-X levels the pits and scratches, making the surface very slick. I happen to actually work for the chemical company that makes the rain-x pre-packaged chemicals in bulk, my Black 93 Nissan Pathfinder is the test bed for all of the products in that line. It's a 93, has 190k miles on it and not a spot of rust on it except underneath on the chassis where the products wouldn't reach. And I live in the upper midwest where the winters are long, and very high in sodium and sand. I use it on my brand new car too. My company does pay me to keep the Pathfinder around too, just as an example car. When I am ready to replace the Pathfinder, they will buy it from me. There are people at work who use it on their safety goggles and on all the interior windows in the tank farm and reactor areas because it just makes spills just clean right off. It's good stuff, I have a lot of it in the garage, including the car wash, tire cleaner and almost all the car waxes.
