I wish I had seen your query sooner, but DO NOT use the provided specs. There is only one sure way to determine your size and that’s by measuring your bare feet and using the length of the longest one to determine the correct size. Accurate sizing is critical to get their full benefits and insure a good experience. Vibram used to provide a much better size chart using foot length in inches but, unfortunately, that’s not the chart shown under specs because it’s using U.S. shoe size which, in my case, is wildly inaccurate. I wear a size 10 in U.S. shoe size which, according to the chart means I should buy a 43 or 44, but my longest foot measures 10.5" so I actually take a 42 VFF. And I can tell you, these are made to fit as closely as possible so you need to be as exact as possible, which is why there are so many “good/accurate” charts available online that use your foot measurements. If you’re off by one size you’ll have a bad experience for two reasons. First, each shoe has a heel cup with a low spot to “locate” the wearer’s foot. Second, when your heel is seated properly, you want the toes on your longest foot to be just shy of touching the inside of the end of each toe pocket. Since the best fit is as described, another variable will be whether you want to wear toe socks or go barefooted. The size you get by measuring your feet will be the size you want if you go barefoot, you should go up one size if you plan on wearing Injinji, or other brand of socks. I only go barefooted. I tried toe socks and hated them because they ruined the whole barefoot feel for me. With proper fit and without socks I forget I’m even wearing them, but with socks I was constantly aware of them because the socks allowed my foot to move somewhat inside the shoe, even if only slightly. I know others have written they like socks so … to each their own.
HERE is one site I found that shows a more accurate size chart. There’s also a number of YouTube videos, LIKE THIS ONE in which Vibram shows you how to measure your feet for their shoes and still others, LIKE THIS ONE that talk about what to expect if you’re even one size off. You can find these sites by searching for “Vibram Five Fingers Sizing”. I hope this information helps. But again, I strongly encourage any first time buyers to measure their feet, as described in the YouTube video, to determine their size rather than use the provided chart.