Green Lantern Ring

This is my whack at a three part Green Lantern ring. I made it for a friend who is size 11.5 (US/Canada units), put another way, the inner diameter is 20.6mm.

If you want it in a different size, I am not sure I am ready to parametrize this, but shoot me a message and I can share the 123D file and walk you through my math.