Audi models A6 and A8. The Neckarsulm factory is also home of the "quattro GmbH" (from November 2016 "Audi Sport GmbH"), a subsidiary responsible for development and production of Audi high-performance models: the R8 and the RS model range. Modern era The new merged company was incorporated on 1 January 1969 and was known as Audi NSU Auto Union AG, with its headquarters at NSU's Neckarsulm plant, and saw the emergence of Audi as a separate brand for the first time since the pre-war era. Volkswagen introduced the Audi brand to the United States for the 1970 model year. That same year, the mid-sized car that NSU had been working on, the K70, originally intended to slot between the rear-engined Prinz models and the futuristic NSU Ro 80, was instead launched as a Volkswagen. After the launch of the Audi 100 of 1968, the Audi 80/Fox (which formed the basis for the 1973 Volkswagen Passat) followed in 1972 and the Audi 50 (later rebadged as the Volkswagen Polo) in 1974. The Audi 50 was a seminal design because it was the first incarnation of the Golf/Polo concept, one that led to a hugely successful world car. Ultimately, the Audi 80 and 100 (progenitors of the A4 and A6, respectively) became the company's biggest sellers, whilst little investment was made in the fading NSU range; the Prinz models were dropped in 1973 whilst the fatally flawed NSU Ro80 went out of production in 1977, spelling the effective end of the NSU brand. Production of the Audi 100 had been steadily moved from Ingolstadt to Neckarsulm as the 1970s had progressed, and by the appearance of the second generation C2 version in 1976, all production was now at the former NSU plant. Neckarsulm from that point onward would produce Audi's higher-end models. The Audi image at this time was a conservative one, and so, a proposal from chassis engineer Jörg Bensinger was accepted to develop the four-wheel drive technology in Volkswagen's Iltis military vehicle for an Audi performance car and rally racing car. The performance car, introduced in 1980, was named the "Audi Quattro", a turbocharged coupé which was also the first German large-scale production vehicle to feature permanent all-wheel drive through a centre differential. Commonly referred to as the "Ur-Quattro" (the "Ur-" prefix is a German augmentative used, in this case, to mean "original" and is also applied to the first