Stock rotors are 9.8". I have a pic comparing the stock, jdm, and 300zx brakes, but my website is down. Rotors are as big as Z-brakes, just not as thick. JDM 180sx pads actually have more surface area than Z-brakes. If need an upgrade on 4-lug and don't want to worry about wheels that clear large calipers, this is what you want!