Here are the rings and I've numbered them 1-5. You can download the files here. I've attached STL files and also included hyperlinks below so you can download straight into 123D and start customizing your ring right away!
I'll be using ring design #5 to show you how to personalize it with your initials. Free 123D Download Ring #1: Ring #2: Ring #3: Ring #4: Ring #5: