so if you wear a sz 8 and your feet are wide or swell like mine do then you will want the 9/10 . Ive owned a pair of ATH-M50xs, another well known (and probably best) set of headphones you can get for your money, which is also made by Audio Technica. But the biggest surprise is the midrange. I have no regrets with this purchase. No itching! Hes helped thousands of people know themselves and love their work more. It works almost flawlessly. If you are an avid lake or beach goer, these are not the shoes for you. Easy installation for first time user. Assembly instructions were difficult.