Most of the rings can be specified in a Regular Profile, More Round, Less Round, or Flat Profile.  The Regular Profile is a very comfortable ring, and is used the vast majority of the time.  It is .085" (2.16mm) thick in the center, which is a little less thick than some of the titanium rings I've seen at jewelry stores.  The inside has a straight bore, but the outer edges have generous elliptical radii, so the ring has the feel of a Comfort Fit without the sizing problems or the rocking on the finger issues.  The Flat Profile rings are usually .070" (1.78mm), but can be specified in More Thick or Less Thick.  The rings were drawn to scale using a 7mm width.