Citroën purchased this fully unitary body design for the Citroën Traction Avant. This high volume, mass production car was introduced in 1934 and sold 760,000 units over the next 23 years of production. This application was the first iteration of the modern structural integration of body and chassis, using spot welded deep stamped steel sheets into a structural cage, including sills, pillars and roof beams. In addition to a unitary body with no separate frame, the Traction Avant also featured other innovations such as four-wheel independent suspension, and front-wheel drive. The result was a low-slung vehicle with an open, flat-floored interior.