Girodisc Porsche 991 GT3, GT2RS, GT4RS PCCB Front Iron Rotor ConversionThe Girodisc system is a direct replacement for the OE disc however you must use the same pad shape that is used on the 991 GT3 that came with the iron rotors from the factory. The annulus (pad swept height) of these pads is smaller than the large PCCB pads, this is done to keep the rotor weight at a reasonable level and allow far better pad selection. If we manufactured a rotor with the same annulus as the OEM PCCB rotors they would be unnecessarily