it's either what Raynman said, or sometimes it's just a lug nut extender, because a lug nut wrench won't fit around it while it's on the wheel. it's essentially a deep well socket for your lug nuts.
Got it. Thanks for the clarification. The damn things arrived at my house just about 24 hours from the time I hung up the phone. Now if Tirerack shipped the right wheels and tires AND they fit, goodnews story for all.