I have decided on a date to propose to my girlfriend and am very excited. I have done my research on diamonds and will start shopping for one in the next week or two. Now it comes to the ring. I really want to get her a tension mounted ring, but my friend told me they have to size her. My girlfriend doesn''t want to be involved in choosing the ring or any of the process and wants to be suprised (the proposal will be a big suprise, very romantic - a dolphin is going to help me give her the proposal). I know her ring size and would like to design it based on that, will that work or do I have to take her in to get her measured?