Saturn replaced its entry-level S-Series models for 2003 with larger, more powerful subcompact Ion sedans and a unique four-door coupe. Sedans and coupes retained the brand's trademark dent-resistant plastic bodyside panels. Both body styles were nearly the same length, and shared a wheelbase about an inch longer than that of the S-Series. Compared to their S-Series predecessors, the Ion sedan was longer overall by 4.5 inches, and the coupe by 6.4 inches. Both were taller by more than 2 inches. Saturn called the coupe the Ion Quad Coupe, for its unique configuration of two rear-opening half-doors behind the front doors. The rear doors would not open or close independently of the fronts. A new four-cylinder produced 140 horsepower. A five-speed manual transmission was standard. Two automatic transmissions were available: a continuously variable unit (CVT) on coupes, and a conventional five-speed on sedans. The CVT featured near-infinite ratios. Head-protecting curtain side airbags were optional. Torso side airbags were not available. An ABS/traction-control system also was optional. All Ions had front-disc/rear-drum brakes. Primary instruments sat in the center of the dashboard, rather than directly in front of the driver. Split folding rear seatbacks were standard, and the coupe's front passenger seat could fold forward to create a continuous 10-foot-long storage channel. Sedans ascended through Ion 1, 2, and 3 trim levels. Coupes came in 1 and 2 form, equivalent in equipment to the 2- and 3-level sedans. Air conditioning was standard, except for the 1 sedan. Leather upholstery was optional on 3 sedans and 2 Quad Coupes. Wheel sizes were 14-inch for the 1 sedan, 15-inch on the 2 sedan and 1 coupe, and 16-inch alloys for the 3 sedan and 2 Coupe. Both the coupe and sedan could be fitted with interchangeable strips of body trim, tracing the arc of the roof. Available through Saturn dealers, these contrasting-color "roof rails" could be matched to interchangeable interior trim pieces. Saturn's Ion competed against the Ford Focus, Honda Civic, Hyundai Elantra, Toyota Corolla, and Volkswagen Jetta/Golf.