The Subaru WRX is powered by a 2.0L turbocharged "boxer" 4-cylinder engine. In standard WRX guise it produces 268 hp, which is fed to all four wheels through a 6-speed manual transmission. The WRX STi is also powered by a 4-cylinder engine with a turbocharger, but in the STi the displacement jumps to 2.5L and output is rated at 305 hp. The STi features the same all-wheel drive system and a 6-speed manual combination that is so potent in the standard WRX. A continuously variable automatic transmission is available on the WRX but not on the STi version. The WRX comes in three trims, standard, premium and Limited. Standard WRX models come with 17-inch wheels, a 6-speaker sound system with iPod connectivity and support, SiriusXM satellite Radio, an automatic climate control system, a 4.3-inch LCD screen and a backup camera. The premium WRX model comes equipped heated front seats and mirrors, a power moonroof, fog lamps and an aero package that includes a rear spoiler. Limited trim includes everything that comes with the premium trim as well as an 8-way power adjustable driver's seat, leather trimmed upholstery and LED headlights. The STi differentiates its self from the standard WRX with a more aggressive exterior, featuring a unique hood and more aggressive fender flares. The bumpers are also more aerodynamic, giving the STi the part of a high performance vehicle. Backing this impression up are lower, stiffer springs, bigger brakes and bigger wheels. The STi comes loaded with features and in only one trim level. Standard features include 18-inch wheels spread over massive 13-inch front brakes, a 60/40 split folding rear seat, a leather wrapped flat-bottom steering wheel, a 3.5-inch LCD screen mounted in the instrument cluster and a dual-zone climate control system. Options on the STi include a navigation system with a 6.1-inch LCD screen, a Harman/Kardon premium sound system, an 8-way power adjustable driver's seat and a power moonroof. Safety features include anti-lock brakes, traction control and stability control as well as the confidence of Subaru's symmetrical all-wheel drive system. Brakes have also been upgraded for 2015 with even the standard WRX receiving bigger front brakes than the outgoing model.