The GiroDisc 2-piece rotor system is a direct replacement for the OE rotor, no modifications are necessary. The disc will bolt directly to the car and work with OE calipers perfectly. Once the Girodisc system is in place, simply replace the cast iron rotor ring when needed. The average Girodisc 2-piece rotor is approx 2kg lighter per rotor then the stock units. This reduction in rotational and unsprung weight allows for quicker acceleration and suspension response.