The Mercedes Benz 300SL is a significant milestone in the history of sports cars. It has a birdcage-shaped steel pipe space frame, which is modeled after the W196 and Wl96R (300SLR). These models were genuine Grand Prix/racing sports cars that dominated racing in the mid 1950s. The strength and structure of the car had to be placed high inside the doorsills, leading to the invention of the gull wing door. This also allowed the earlier coupes to have lower roofs. The Roadster version was introduced in March l957 as the successor to the 300SL Coupe. It lost the spartan quality of the 300SL Coupe and evolved into the most sophisticated super sports car of its time. The interior and exterior design were extremely refined and the handling made easier with improvements to the suspension. It also became simpler to get in and out of the car by lowering the side sills after the gull wing doors were eliminated.