TLDR; Much lower in cost than official Lego Steering parts, absolutely no wobble in the linkage, and whatever colour you desire!
Update: Final Revision! I challenge anyone who purchases this to come up with any impovement that can be made; I assure you it won't be easy, so I'll even send you a coupon over paypal so you can purchase your improved version for free.
This hub is designed to function as a non driven hub for the front wheels of a rear wheel drive Lego vehicle. It fits around a set of two 5x13x4mm (or 5x10x4mm) radial bearings (I purchased mine from ebay at 10 pieces for $3). The bearings to be used in this have an inner diameter of 5mm, allowing lego axles to fit through perfectly, and be held tight with just a layer of tape or glue around the axle. I also designed the hub with the steering linkage offset from the kingpin by a ratio of 3:1 (length to width) for a basic ackermann steering geometry. (used to prevent wheel slip)
It comes as a set of two that can be easily clipped apart with a hobby knife, or some thin scissors. The purpose is to include both left and right hubs, while keeping the cost lower since number of items is a factor in shapeway's pricing. The surface they're attatched at isn't vital, so just clean off whatever excess you like to without cutting into the necessary structure too far.
Fun fact: These hubs were created to replace the age old Lego steering hubs (part x873c01 on bricklink) which are being sold for 8+ CAD (used), and 12+ CAD (new) per hub. This new and improved replacement only costs (depending on finish and size) 6.89-8.46 CAD for a pair, then ~1.2 CAD on top of that for the 4 bearings. That's 4.05~4.83 CAD per HUB!
Therefore, it's still far lower in cost, has much less wobble in the parts, and comes in whatever colour you desire!