The WRX STI tS was based on the 4-door WRX STI model and developed as an STI complete car which featured STI's unique component specifications in the exterior, interior and chassis, providing an opportunity to enjoy the pleasure of driving and the joy of ownership even more. It sported a carbon roof developed jointly by Fuji Heavy Industries and Toray Industries, which had been introduced in SUBARU production vehicles for the first time. Its front and rear dampers and special coil springs tuned by STI, Flexible Tower Bar Front, and Flexible Draw Stiffener, along with a Flexible Support Rear and rear suspension links were installed for improved handling that made the driver feel good. Furthermore, components such as bushings were also finely tuned. In addition to the carbon roof, an aluminium hood was adopted to achieve both weight reduction and performance enhancement. Other features included a front under spoiler, STI 18-inch aluminium wheels, side sill plates with the ‘tS’ logo, a steering wheel with the STI logo, a push engine switch, and a RECARO front seat; optional for the automatic transmission model while leather seats came standard. Additionally, the manual transmission model was equipped with a ball bearing turbo charger to increase turbo response and a special ECU to increase the maximum torque by 0.8km-g. A 2.5-liter turbo engine automatic transmission model (A-Line) was also available.