I got this clog and loved the look of it but knew right away it was too big.  I am a size 7 but the sizing was for a 7 to 7 1/2.  It was way too big for me and there was nothing smaller.  Such a bummer as I loved the look and they seemed like they would last.  Birkenstock should work on the sizing, for the price you pay one should be able to get an exact fit.