I am breaking in a pair of Quest 4D 3 GTX size 11.5 for a trek in Oct. I am a size 11 normally, but want room for wool socks. The Quest 4D are very comfy, but they are too hot to wear in summer weather. So, I bought the XA PRO 3D for my summer conditioning in 11.5. I slipped them on, feeling comfortable so far, but wow! When I stood up my toes ended up being too close to the front of the shoe, my right toe was actually lightly touching the toe of the shoe. I played around with positioning the OrthoLite footbeds; hoping there was a weird miracle in these adjustments.... Nope, unwearable. Too big a risk of a lot of pain. I am returning these for a size 12. So, in my experience these run very small, or I got an 11 marked as an 11,5? I would recommend these, but hate to think I need to tell someone they need to order as much as one size up...