AR or Aspect Ratio is used in chain maille to describe the ratio between the Inner Diameter (ID) of a ring and the Wire Diameter (WD) that the ring is made in.
Why is this important and why do I need to know all this? Understanding AR will help you calculate easily the ring sizes you need for each weave. In chain maille one ring size does not fit all, and if you have the ideal AR of a weave, or the ability to calculate it, then you are well on your way to finding that perfect ring