Why? Why would Trek have any better quality control? You clearly don't know much about manufacturing processes. The reality is that most of the generic ebay stuff is being produced in the same factories with the same materials to the same specs. It's a very lucrative business for them to product good quality product. It probably costs them a couple dollars to make these stems. Ihave the postage stamp on it, I should do the conversion on the yen to dollars and see if they are also making additional profit on the shipping costs. ebay is free to use with a small percentage being taken for fees but otherwise they don't have a lot of expenses.