Dont have specs but ..... The location of the end gaps between the various ring is relatively unimportant as the will move around anyway. Spread them out evenly..The important part is the gap is big enough to avoid touching when fully heated up. You can find rings where the ends are beveled so that they overlap and end gap is not an isssue. Check out racing suppliers like Summitt. If you are to adjust end gap, a good file will do it. Do not use a grinder or other high speed device. You will heat the end up and possibly change metal temper. They are pretty hard alloy, so a good file and patience are needed. Also, make sure no burrs, sharp edges are left.