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 WarningFront Seat Track Synchronization
The fore/aft manual adjuster is composed of an inboard track assembly (5),
and outboard track (4) assembly, and an adjuster handle (1).
Each track assembly is made of an upper track (2) and a lower track (3). Both
tracks need to be aligned prior to installing in the vehicle.
To align t ...
Installation Procedure
Remove rear end upper panel extension (1) from service part.
Cut
Cut the body side inner 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 sectioni ...
Floor Carpet Drying
If the carpet or the pad or insulator is wet, use the following criteria for
drying or for replacing the components:
For a 1-piece carpet assembly bonded to a cotton or a fiber padding,
replace the entire assembly
For a 2-piece carpet assembly with a cotton or a fiber padding, replace
...