The base Sierra comes with 17-inch steel wheels, chrome bumpers and grille, air-conditioning, cruise control, power windows and door locks, a tilt steering wheel, cloth upholstery, rubber floor covering, a 40/20/40-split front bench seat and a four-speaker AM/FM sound system with a 4-inch color display and USB and auxiliary inputs. The SLE adds stainless steel finish wheels, deep-tint glass, an E-Z lift/lower tailgate, LED cargo box lighting, power/heated mirrors, keyless entry, a rearview camera, Bluetooth phone and audio connectivity, adjustable driver lumbar support, a leather-wrapped steering wheel with audio controls, OnStar telematics with 4G LTE WiFi capability, a color driver information display and an upgraded IntelliLink audio system (with an 8-inch color display, satellite radio, Pandora radio, a CD player and voice control functionality). Optional on the SLE is the Carbon-22 Edition, which features unique 22-inch alloy wheels, a rear locking differential (2WD models only), foglamps, a black grille surround, tubular side steps, a trailering package, a 10-way power driver seat, dual-zone automatic climate control, a tilt-and-telescoping steering wheel, remote vehicle start, remote garage opener, a rear-window defogger and a 110-volt AC power outlet. Standard safety features on the 2015 GMC Sierra include antilock disc brakes, traction and stability control (with trailer sway control), front and rear seat side airbags and side curtain airbags. Also standard is OnStar, which includes services such as automatic crash notification, roadside assistance, remote door unlocking and stolen-vehicle assistance.