I wear a size 8 and bought the size that fits sizes 6.5 - 8.  While they do fit in my shoe, the arch support is sitting mostly under my heel instead of being centered under my arch.  Very uncomfortable.  I tried trimming them down a bit so I could push them forward, but the gaps at the end of the shoes then feel weird.  I switched and got some Powerstep Pinnacle Maxx insoles instead.  They are made for specific shoe sizes (I got ones for 8-8.5) instead of covering a range of sizes and they fit perfectly.  The Superfeet feel like they are a well made product; I just think they would be better if they made more different sizes.