AS said on here before theres a company near me that puts parts into ford/vxl/nissan/etc and so now you see-its like unipart years age thats why I laugh when people say must be GM?? its usually only the box!! I work now for a company that makes the boxes as got fed up being a nurse-hours etc
Its usually not as simple as that, as the GM (Rover/Fraud/French shite/whatever) often do NOT allow the OE manufacturer to sell that part, written into the contract. They are allowed, sometimes, to make aftermarket ones, but not to identical specification. Unipart did have an agreement, certainly with AR, to produce some OE parts for selling into the trade, although I believe that expired in the Rover days, possibly even pre BMW. So, its only really in exceptional circumstances that it is just the box/sticker/packet.
As a community, we have a good enough grasp to know what pattern parts to recommend, and what to avoid, and what absolutely must come from a dealer. We have that experience, knowledge, and understanding. Additionally, we know when to recommend pattern over GM genuine parts, based on price and quality. For example, GM "Tradeclub" pads are slightly cheaper than the Unipart ones, but far, far better. Contiech and Gates V6 cambelt kits are of similar quality to GM, but far more reasonably priced. Nothing comes close to a genuine GM air filter for the Omega.