[A26B]

Obviously, I don't know how GM does it and I'm darn sure not a GM size company either....BUT...... When I spec an item or a job, it's done so with all relative parameters which include not only size & material, but finish, relative ASME, API, and other engineering, material & manufacturing standards. Done right, there's nothing left to vary except price. Quality follows the specifications. I would expect GM does this also.