the first pair i bought had a black rubber insert and is much better than the one that comes in these.  I actually keep using the black rubber insert and just buy new crocs.  The inserts in these tend to wear in and dont absorb the same as the rubber.  But love the shoes so much I work in them doing construction.  Low impact on the body.  Easy to take on and off for those fussy customers.  I am on my 7th pair this year.  Not osha approved for construction though!