For example, doctors use 3*8, county officials use 4* 10, and so on.
It is impolite to wear 9. 9 is a number that only emperors can use, so there is no size of 9.
However, there is no such requirement now. If you want to pay attention to the size of the plaque, you can go to the customized place and ask clearly. People make it every day.
If you don't want to do it, you can do it, but the size of the plaque is generally standardized, so it is not good to change it for others.
From ancient times to the present, only plaques are exquisite.