Nuns wearing wedding bands?

On a recent trip a nice nun took a picture of my family. I noticed that the nun was wearing a wedding band on her left hand. I have a vague recollection of reading somewhere that nuns are considered to be “brides of Christ”, which leads to my two-part question. Do all nuns wear these symbolic wedding bands? If not, is this practice limited to certain religious orders, or is it an individual choice?