I have size 10.5 feet. After reading that you could drop down a size with the thermoflex liners, I tried a pair of 27's (AF-600). Big mistake, there was no way they would fit without a lot of pain, even with a good bootfitter. I've had Raichle 324, 423 and 413 all in size 28-28.5 now and they're perfect, even after some packing out. If comfort is important to you I would suggest nothing less than 28 if you have 10.5 feet.