My girlfriend mentioned that she has a ring sized of 5mm, what size is that with American sizes. She is orginally from South America and I want to buy her a nice gift when i go and visit her, but I want it to be a suprise. I don''t want to ask her what ring size she is again because I asked her a while ago and she has since forgotten. I thought about taking her to a Jewler when she was here but just didn''t so stupid!!!!!!!!!! Any help anyone can give me would be greatly appreciated.