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 WarningTiming Chain Idler Sprocket Installation - Left Side Valvetrain Valvetrain Timing Timing Belt/Chain
Ensure that the left camshaft intermediate drive chainidler-(2) is being installed. The recessedhub-(3) and the larger sprocket of the left camshaftintermediate drive chain idler is installed outward. The raised huband the smaller sprocket of the left camshaft intermediate drivechain idler is instal ...