I once bought a set of aftermarket wheels for a Honda that I had and the company that sold them insisted that the wheels where lug centric and didn't need hub rings. No matter how often I had them balanced, there was a steering wheel vibration that wouldn't go away. I caved and bought a set of aluminum hub centric rings from
www.discounttire.com and installed them and the vibration disappeared never to return. They cost $12 for all four with free shipping. Call them and tell them your car make and wheel choice (if it is a stock wheel) and they'll look up the hub and bore sizes and spec the ring. If you use aftermarket wheels, you'll need the bore size.