Brand New, Top Quality, Aftermarket, Solid Stainess Steel Rotating Bezel Bease Ring for Rolex GMT-Master II Watches.  They are made for a Rolex Submariner model (it will not work with vintage Rolex GMT-Master and won't work with Submariner models).
 
This item is guaranteed to fit your Rolex GMT-Master II watch which has a sapphire crystal.
You will not be able to tell the difference from the original.