GirsoDisc Porsche Cayman/Boxster (981) Front RotorsThe Girodisc system is a direct replacement for the OE disc with the addition of our provided caliper spacers. Our rotor is slightly larger than the OEM rotor at 340mm versus 330mm providing greater braking force and cooling capacity. The central hat section of our rotor is made from strictly U. S. sourced 6061 T6 aircraft specification aluminum. The disc is made from our own proprietary cast iron, poured in the USA and machined from start to finish