Most people have, on the back of their head, a bump called the occipital bun. Most, certainly not all but most, FUT scars I have seen on people’s heads rest on that bump along the occipital ridge. Whatever the science behind that is I’m not sure of, however, that is usually where it rests. Maybe it has to do with the skin being better able to stretch and pulled together to be sutured. I don’t know. Speaking in terms of length, not width, scars can definitely be shorter or longer back there, as gillenator said, depending on how many grafts are required and how many grafts per cm2 you have back there. Do a google search of, “hair transplant scars”, and you’ll see a variety of scar lengths. A good doctor will cut the old scar out along with the new tissue being removed so that you are left with one remaining scar after the surgery.