At the end of the 1960s, two future-oriented plastic sports cars were created in Germany that many a car buyer would have loved to have in their garage. Together with BMW, Bayer developed a platform that could have been fitted with different bodies; the Delta 1 Roadster was an uncompromising sports machine that could rival many a Porsche. Despite interesting approaches, both cars never went into series production, although they were thought to have good chances of doing so. This historical comparison test by 'hobby' magazine reveals the secrets of the two prototypes and explains the technology, illustrated with historical pictures from the time.