Hub rings are used to fill in the gap between the hub bore of the wheel and the hub of the vehicle. Aftermarket wheels are lug centric and not hub centric similar to OE wheels that came on your vehicle from factory. Lug centric means the wheels are centered onto the vehicle using the lugs.
Aftermarket wheels typically have a larger hub bore to fit more vehicles as different vehicle manufactures have different hub sizes. Hub rings are not load bearing and once the lugs are tightened, the hub rings do not support the weight of the wheel itself.
If you’re installing aftermarket wheels, you can use hub rings to close the gap and minimize the chance of vibrations but they are not required.
If you're not sure whether you're needing hub rings, feel free to submit a request Here