Some manufacturer’s, like Audi, BMW, Dodge, and Volkswagen require knowing whether you have vented rotors or solid rotors, in order to get the correct rotors for your vehicle application. That is because if you a solid rear disc, it could take one front rotor, but if you have a vented rear disc, it could take a different front rotor. This usually pertains to just the rear rotors, because solid discs are usually found on just the rears. There are some vehicles that have solid front rotors, but they are very few and usually on older vehicles. The friction surface of a vented rotor consists of two metal discs held together with vanes of metal which creates tunnels that let the heat escape. We call those cooling vanes. With the solid rotor, the friction surface consists of only one metal disc. This greatly reduces its ability for cooling. It is a common misunderstanding that you can choose whether you get a solid or vented rotor, this is NOT true. We can only offer you Original Equipment Replacements. So if your vehicle came with a solid rotor, it will be replaced with a solid rotor. Keep in mind that we can drill and slot both solid and vented rotors.