I ordered 11.5 while wearing it. It fits true to size. The back is relatively low. Pretty comfortable from the start. Also very quiet, you can walk in these boots as quietly as you would with bare feet. Update: After 1.5 months of daily use, the rubber relief on the bottom has clearly worn out. However, it looks like it could take another 2-3 months. Update 2: The floors wear out completely after 2.5 months of daily use.