An expansion on the sport-themed Audi S4, the RS4 is imagined with a pure performance focus. Adhering to its premise of being a low-production, high-performance car, the Audi RS4 was sold in the United States for two years starting in 2007. Compared to the S4, the Audi RS4 featured a wider fenders and special 19-inch wheels. The biggest defining point of the Audi RS4 is the 4.2-liter V-8 engine that produces 420 horsepower. A six-speed manual transmission provided a transition of power from the engine to the quattro all-wheel drive system. Inside, the front drive and passenger seats have been supplied by Recaro. Debuting as a sedan, the 2007 Audi RS4 was expanded to include a four-passenger Cabriolet model for the 2008 model year. At the time, the 2008 RS4 Cabriolet was the most powerful convertible Audi had produced. While there have been three iterations of the Audi RS4 introduced in Europe, the 2007 and 2008 model year RS4's are the only versions that were imported to the United States.