For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningCompass
The vehicle may have a compass display in the Driver Information Center (DIC).
The compass receives its heading and other information from the Global Positioning
System (GPS) antenna, StabiliTrak, and vehicle speed information.
Avoid covering the GPS antenna, located on the roof, for long perio ...
Wheel Alignment Measurement
Steering and vibration complaints are not always the result of improper
alignment. One possible cause is wheel and tire imbalance.
Another possibility is tire lead due to worn or improperly manufactured tires.
Lead/pull is defined as follows: At a constant highway speed
on a typical straight ...
Collision Repair
Specifications
Point-to-point measurements are for reference only. All measurements are
given in millimeters. Use these measurements for diagnosing
and estimating. Point-to-point measurements are duplicated with tram bar
pointers set at equal lengths. All die marks, holes, slots, and
fast ...