after reading reviews and recommendations by previous buyers, I purchased a size 13 Crocs Mens Mammouth Evo Clog. They where huge and had to return them.  My regular size shoe is an 11 so I proceeded to purchased a size 11. When they arrived, they were slightly larger than what I felt comfortable holding onto, so I returned them as well.  I then purchased and received a size 10 and they fit just right. My feet were so happy, they drifted off into a snug slumber. Hope you enjoy yours!  I since purchased a pair for my sister and she is thrilled as well... womans size 8 fit snug and she wears an 8 1/2 shoe size.