Ordered a twin size.  I was worried when I got it all unwrapped because it was folded in half and I wasn’t sure if those crease would actually go flat.  Less than an hour it was already laying flatter.  It is on a very firm mattress and it sure helps to give you a nice cushion without taking away from the support needed.  The cover is nice and soft too.  However my mattress protector does not have deep enough pockets, so for now it’s just under the sheets.  It says to wait a few days to allow it to fully expand, however within a few hours it looked perfect.  So far, seems to be a great addition to the bed!