Strangely, the left shoe rubs and blisters the back of the achilles'.  So, to wear these shoes I have to put an ugly Band-Aid to prevent the rubbing.  The right shoe does not cause this problem.  I have other crocs shoes (Adrina's, Cleo's, classic's) that have never given me a blister.  It never occurred to me that this could happen with Crocs.  I keep looking at the achilles' band at the back of the shoe (it's the rear band near the heel) hoping to find some defect.  I see nothing defective, but still I have to wear the Band-Aid to prevent the blistering.  Ouch!!!  If I could ship these shoes back, I would.