I am another long-time (10+ years) user of New Balance shoes who finds that the 510v2 shoe doesn't fit my feet. The toe-box is generally too small, much smaller than other New Balance models that I wear regularly. The size differences seem random. I normally wear a 10.5 wide, which didn't fit me at all.  The 11 x-wide size was wide enough, but so short that my toes curl at the end. So I tried an 11.5 x-wide, which was long enough, but as painfully narrow as a medium width shoe. So if you've found a size that fits you properly in this model, that's great, but don't depend on the size of this shoe to determine a proper fit. I've given up trying to find a size that fits in the 510 model.