The HUB CENTRIC RING installation order:
1. First insert the ring in the alloy disk (wheel).
2. And then place the wheel(disk) on the wheel hub.
How to measure by yourself?
For right choice of alignment rings you need just two sizes - centering bore diameter desired for the installation disk (DIA), and hole diameter regular disk (diameter of the hub).
To measure the diameter of the hub and diameter of the disk central bore you need Calipers
To measure diameter of the disk hole You must have Calipers without depth probe or :
1. unscrew the two bolts from the calipers
2. remove the second part of the calipers
3. remove the depth probe (DEPTH PROBE - makes difficult to measure accurately)