They are also the same compound as the fronts, even though they are 1 piece. I have driven back to back in very similarly set up Zs with the main difference being Brembo (stock size) slotted cross drilled rotors VS. SZ (stock size) front and rear rotors. There was a noticeable difference in initial bite, "feel" & stopping distance, etc. Needless to say, I was surprised. Pleasantly surprised that rotors can have such an effect. I'm looking to up grade my braking system soon and I'm leaning towards the SZ rear rotors over the StopTech 13" rear kit (with the addition of the StopTech 13" front kit). Additionally I did run the SZ front 2 piece rotors for a couple of months (a friend lent them to me to show me how much difference there really was) with great results. IMHO there is a difference that is noticeable & worth it. I hope it helps.
