You probably wont need one, but here's a secret - not all seat belts are the same length! I know - I have measured them myself since I usually, but not always do. A Flight Attendant once explained it to me - they have to check the seat belts quite frequently. When there are small issues on the ends of them, they sometimes simply cut them a little shorter. Some sometimes you get stuck in a seat with a really short belt. I have gotten to the point where I usually ask for one even if the belt technically fits but is tight, just for the comfort of it. almost every flight I have been on at least a few passengers ask for them.