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Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningAnti-Corrosion Treatment and Repair (Base)
Warning: When applying sound deadeners, or anti-corrosion materials
due care and preventative measures must be exercised to prevent
any material from being sprayed into door and quarter panel mechanisms such as
door locks, window run channels, window regulators and
seat belt retractors, as wel ...
Installation Procedure
Drill 8 mm (5/16 in) for plug welding along the edges of the service
panel as noted from the original panel.
Clean and prepare the attaching surfaces for welding.
Apply one-part windshield urethane adhesive as noted
from the original panel.
Position the roof ...
Waterleak Test Preparation
GM vehicles are designed to operate under normal environmental
conditions.
The design criteria for sealing materials and components takes into
consideration the sealing forces required to withstand the natural
elements. These specifications cannot take into consideration any artificial ...