was offered with the 6-speed manual transmission. In 1997, the Spider was offered with the F1 transmission available as an option. The Spider proved to be the second-most popular F355 model, with a total production of 3,717 units, of which 2,664 were produced with the 6-speed manual transmission and 1,053 were produced with the F1 transmission. F355 GTS In 1995, Ferrari introduced the GTS model to the F355 family. The GTS model was based on the Berlinetta but offered a removable "targa-style" hardtop roof, which could be stored behind the seats. Other specifications were identical to the Berlinetta. A total of 2,577 GTS models were produced, with 2,048 delivered with the 6-speed manual transmission and another 529 with the F1 transmission. F355 Challenge In 1995, Ferrari introduced a race-ready F355 Challenge model for use specifically in the Ferrari Challenge race series. The Ferrari F355 Challenge model was developed by starting with a standard Ferrari F355 Berlinetta and modifying it with a US$30,000 factory-to-dealer supplied kit. The initial 1995 cars came with factory fitted cage mounts and without carpets. Each year, the cars arrived with more and more factory fitted race parts, culminating in 1998 with full-evolution cars which were supplied as virtually complete race cars except for some parts such as the rear wing, which still needed to be fitted by the dealer. The kit initially was more substantial than the 348 Challenge and the engine, gearbox, and shock-absorbers were sealed with special tags to prevent unauthorized modifications. The kit included the following components/modifications: Roll-cage Racing bucket seats Safety harnesses Fire extinguisher Engine cut-off switch Manual radiator fan control and upgraded fans Competition steering wheel Lightweight exhaust Rear wing Competition clutch Upgraded 14-inch Brembo brakes (carried over from the F40) 18-inch Speedline magnesium wheels Pirelli racing slicks Solid suspension bushings and competition springs Front and Rear brake cooling ducts Challenge black perforated rear grille (halfway through the 1995 season to get extra air through the engine-bay) Lightened front bumper Front and rear tow hooks The F355 Challenge shares the same engine and physical dimensions as the standard F355 Berlinetta. 108 cars in total were produced, all of which were equipped with the 6-speed manual transmission. Although some sources indicate that over 300 cars were subject to the Challenge conversion, yet this claim remains unproven. There were 18 RHD cars imported by Ferrari UK and modified by MHT. A further 10