Intriguing, yes? Here's a quote from the article at PCWorld: Microsoft will send you a free Surface Pro 4 spacer for your old Surface Pro 3 dock "You’ll need to visit Microsoft’s Surface Online Support Center and click the “Replace an Accessory” button. Register your Surface Pro 4 tablet if you haven’t already. You should then see the option to have Microsoft ship you the free spacer. (Microsoft will reportedly charge $6 for shipping.) For some reason the serial number attached to our Surface Pro 4 wasn’t recognized as a valid serial number, probably because it was a review unit."