Please note that we offer 2 piece competition rear rotors as an add-on option for a complete set! RR Racing GiroDisc Porsche 991.1 2-Piece Racing Rear Rotors The RR Racing 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 350mm versus 340mm providing greater braking force and cooling capacity. The Girodisc front rotors are approx 21.0 lbs vs. 24.4 lbs for the stock units. This reduction in rotational and unsprung weight allows for quicker acceleration and suspension response. 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 in house at Girodisc. The rotor utilizes a curved vane design, developed in racing to act as a centrifugal pump to force cooling air through the disc. The rotor and hat have a floating mount system, which utilizes 10 high strength alloy steel drive pins, manufactured by Girodisc in the USA to our own specifications and cadmium plated for a long lasting corrosion resistance. These pins take the load from braking actions while maintaining the axial and radial float between the hat and disc. The pins are secured by class 12.9 cap screws with hardened washers. In order to keep the rotors from making noise when cold, the pins are mounted with anti-noise spring washers on the rotor side which allow the rotor to grow with heat expansion but eliminate the rattle and noise associated with floating rotors. This float also allows the rotor to self center between the pads. Once the Girodisc system is in place, simply replace the cast iron rotor when needed. And of course, in order to ensure the quality of our products, all of our components are made in the USA by Girodisc, including the discs and hats.