My husband is an ER Doctor, and he's been wearing Crocs for work for years.  For some reason the sizing all of a sudden changed without any warning.  He's always worn a size 12 in his Crocs, but these were way too big, and we ended up having to go out to a store, try them on and buy a size 11 instead.  When you change your sizing, you should warn people, especially when they are ordering online!