I think everything McMaster dates to it being a physical book first. They still operate on that same business model, but we have the internet now. The supplied product might change, but it still meets whatever specification is in the catalog that is released yearly. If they could guarantee a TI-83 Plus was what you were going to get they would have put it in the catalog, but they couldn't so they don't. And they STILL operate out of that physical book for some customers, so the website has to match it too. That's my take.