GM Genuine Parts Disc Brake Rotors are designed, engineered, and tested to rigorous standards, and are backed by General Motors. Disc Brake Rotors are metal discs mounted to the wheel hub where the caliper can press the brake pads against the disc surfaces to slow the vehicle. GM Genuine Parts are the true OE parts installed during the production of or validated by General Motors for GM vehicles. Some GM Genuine Parts may have formerly appeared as ACDelco GM Original Equipment (OE).