They're comfortable yet firm.  It looks like they will last a long time.  The bottoms seem pretty solid.  I usually wear 8.5 shoes and i got these in 8 and they fit fine.  My foot falls about 1/3 of an inch from the front and about the same from the back and I think this is the appropriate fit for a flip flop.  To go to the 9 probably would have left me a bit too much room.  They are designed to contour  to your foot.  They are not just totally flat like some other flips I had in the past.  Anyway, hope this helped!