This is my second pair of Havaianas - love them!  They are the most comfortable flip-flops I have ever worn.  I am a size 8 in US womens shoes, and purchased the size 39-40, the same as my other pair.  They are a perfect fit.  My new pair is gray with silver metallic, and they look very nice with my swim suit.  I wish I had found Havaianas a long time ago.