This Mini Crib Mattress fits our Pack and Play crib perfectly.  Just what we needed since the bottom was not as soft as it was originally.  The mattress lays right on top of the original bottom.  Our toddler likes it as well, he is sleeping on it without issue and seems to be sleeping even better on his new mattress.  It is very well made, the seams sewn well and all are intact.  Tested its waterproof ability, and the water simply wipes right off.