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 WarningBrakes
This vehicle has front disc brakes and could have rear drum brakes or rear disc
brakes.
Disc brake pads have built-in wear indicators that make a high-pitched warning
sound when the brake pads are worn and new pads are needed.
The sound can come and go or be heard all the time the vehicle is m ...
Mild Steel
This information provides repair recommendations and general guidelines for
steel classified as Mild Steel. This type of steel normally has a
tensile strength less than 270 MPa. This includes the common steel names of:
Mild Steel
Bake Hardenable Steel (BH)
Solid Solution Strengthened Stee ...
Installation Procedure
Cut the roof front header panel in corresponding locations to fit the
remaining original panel. The sectioning joint should be trimmed
to allow a gap of one-and-one-half-times the metal thickness at the
sectioning joint.
Create a 50 mm (2 in) backing plate from the unused portion of ...