I don't know the ins and outs, but I'd just be worried about quality. If anything goes wrong with them, your wheel could end up rolling off down the motorway with you in the bushes!
I have no evidence for this incidentally, I just don't like the thought of eBay stuff in such a critical area.
57 Sapphire Black E91 330d M-Sport
Privacy Glass // Leather // Heated Seats // Bluetooth // Blacklines // BMWP Gloss Black Grille // Alpine HiFi // LCI Headlights