These are some models I made of the DC Lantern Corps Rings. These are not anything official, just my interpretation. The models are in millimeters, so scaling them up by 10 will make an inner diameter (finger diameter) of about 13 mm (1/2 inch). I recently added a White Lantern Ring, but it's still in progress, so expect a cleaner version in the future. Black and Legion rings will come eventually, but probably not for a month or so.
Update: I have a newer version of the White ring, with will hopefully print better than the previous version. I found that most printers have some trouble with the starburst pattern, so I tried to get that a little more printer friendly. Please let me know how it does. I have also added a Black Lantern ring, and a Legion ring should be coming soon.
Update 1/31/16: I have just completed and uploaded a Legion of Heroes ring. I haven't printed this one myself, so feedback on the print is greatly welcome. This is the final ring, so it there's anything else you want me to try to make, feel free to send me a message.