Kappa was General Motors' subcompact rear-wheel drive automobile platform for roadster applications. The architecture debuted in the 2006 Pontiac Solstice and 2007 Saturn Sky, and ended production in 2009. These vehicles generally have a "M" in the fourth digit of their VIN. Kappa uses an independent suspension, short-long arm type, in front and rear. The Ecotec engine is widely used, as is a 5-speed manual transmission. A 5-speed automatic has been available since January 2006. In 2002, the Pontiac Solstice Concept was shown in two forms: a drivable roadster convertible, and a design study of a fastback coupe. The Pontiac Solstice was received very well at the 2002 NAIAS. The drivable roadster concept car shown had been cobbled together from many different components, using a heavily modified portion of the Delta and Epsilon. The thinking was that this architecture might be heavily modified and used to produce the Solstice in the near future. It is speculated that when General Motors decided to try to produce the Solstice as a highly styled, low-cost, low-volume niche vehicle for enthusiasts, it became apparent that there were no existing platforms that could be used to achieve the needs of a modern compact rear wheel drive roadster. Therefore, the Kappa platform was developed to provide the necessary structure for a two-seat, rear-wheel-drive convertible. It features hydro-formed rails and a tunnel structure derived from the Corvette architecture and Sigma, and is designed for a short-long-arm suspension for the front and rear. It features rear wheel drive, longitudinal-mounted transmission and front-mid engine. It has been stated by GM that the platform has only been designed to accommodate a single engine: the Ecotec. It has also been stated by GM representatives that this platform was only designed to be left-hand drive. However, there are aftermarket tuners that have already accomplished non-trivial engine transplants in Solstices. Since the Solstice, GM has designed another roadster that looks substantially different, but shares the same underlying Kappa platform: the Saturn Sky. The Saturn Sky was styled after the pattern of the Vauxhall VX Lightning design. There is a European version built on the same platform, essentially a turbo-engined Sky with Opel badging, under the name Opel GT. A GM Korea version of that variant was also produced under the name Daewoo G2x. Three other concept vehicles were built on the initial Kappa platform, and shown at the 2004 NAIAS: The Vauxhall VX