Real wheel add-on wheel for Thrustmaster TX/T500- genuine?

Hi, I noticed someone claiming to be selling a real Momo add-on wheel for the Thrustmaster & wondered if anyone had come across this kind of thing before? It's Ebay item 131216641146 & he claims it will fit straight onto the base? I'm interested in it but don't want to get ripped off obviously. Does a real wheel make much of a difference? Thanks