This is my second pair of Keen Whisper in the same size.  First pair fit perfect--this one is tight over the instep (the top of my foot).  I thought they would stretch out, but I've been wearing them about 3 hours at a time every day for about 2 weeks, and they still are tight.  The back strap is longer too, and slides down off in the back.  My first pair I could wear all day with no discomfort. Not so with these.  I love that these sandals are made for water, and I wash them often.  Not sure I would buy them again at this price.