The recently sold ebay listings are UG extensions, seller has EB extensions. (The crown stops that are used to attach them are a current part, I think the EB extensions are no longer available (they were the more expensive option when they were both available in Europe. I have them myself, and they are a lot more practical if you get a few extra support brackets with the featherkeys and knobs (partnumbers on ekat).
They are also reversible, if there are mutliple people that want to buy 1 (they can also be used in conjunctioni with the mft3, it can slide onto the piece with the angles in lieu of the fence)