The Citroën D series was the sensation of the 1955 Paris Auto Show. With its streamlined silhouette and its hydro-pneumatic suspension (no springs), this car had many features that were ahead of its time. The D series was produced as the ID series which had a manual transmission and cloth interior, and the more luxurius DS series which had leather seats and a shift lever but no clutch (called Citromatic). The D series rides on four struts that are filled with a mixture of hydraulic fluid and nitrogen gas under high pressure. When the car is started, the hydraulic pump pressurizes the system and the car is raised on the suspension. A lever in the cabin allows one to select different ride heights. This same system also supplies operating pressure to the power brakes and power steering.