My wife loves her Giesswein slippers. As I needed a new pair, preferred to buy European rather than Far East (which last around 6 months at most) and also liked the materials used I decided to go for a pair of the Vent. Bought my normal size. Sadly my foot is just too wide and my instep too high. I could not even get my foot in with the insole removed so had to return them. I doubted that going to the next size up would make a difference. Possibly buying a mule style may have been better but I suspected they would still have the same problem. I ended up buying from a competitor (G*m*i*s) and found my normal size fits well (if anything slightly large).