These rings are designed according to your selection and ring size. There is a separate ring size calculator for each person. Please follow the same steps to determine your ring size and select your ring after your gemstone selection.  The benefits of getting a gemstone and a ring at the same time is the energisation will happen uniformly, and you can wear it without disturbing the energised aura during ring making. 

https://www.msastrology.com/ring-selection