The Xterra is available in four trim levels: X, S, Off-Road, and SE. Four-wheel drive is standard on Off-Road, optional on the others. All models are powered by the 4.0-liter V6. Six-speed manual and five-speed automatic transmissions are available. Safety equipment for all Xterras includes an advanced air bag system, which consists of dual-stage front supplemental air bags with seat belt sensors and a front occupant classification sensor. Active safety features that come standard: Vehicle Dynamic Control, four-wheel disc brakes with anti-lock and Electronic Brake-force Distribution.Changes for 2007 are minor, and consist entirely of shuffling content at the various trim levels.