If the center bore of the wheel matches your hub diameter exactly, you don't need the rings. If there is any gap at all, you need them.

Any wheel that needs them is not hubcentric. The ring simply allows the lugcentric wheel to be properly centered on the hub while you tighten the lugs.

Function before fashion. '96 Contour SE "Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998