GeoSpec® Rear Brake Rotor by Dynamic Friction Company®. Quantity: 1 Per Pack. DFC is excited and proud to introduce our newest short line of premium corrosion-resistant brake rotors – DFC GeoSpec® Coated Brake Rotors. Specially coated with a patented paint to form a durable and attractive silver-gray finish that fights rust far better than other conventional paint or zinc coatings.