I own the XVI, but none of the other shoes. I wear a size 11.5 street shoe and the size 11 XVI fits me well. A size 11.5 might work well too, someone with a wide foot would almost definitely need a size 11.5. I hope that comparison helps. Actually now that I think about it, Five Ten sizing seems pretty standard across most of the models/lasts that I've tried. If I want a tight fit I go with a size 11. If I want a more loose fit I bump to 11.5. I have the Quantum's in a size 12 since the sole is super stiff and I bought them for all day multi-pitch comfort.