This is a very comfortable gel mattress.  It comes all rolled up, and, upon unpacking, I rolled it out to plump up.  It did indeed plump up after 2-3 hours.  A few hours later I noticed a smell in the room from the mattress.  It only took another couple of hours to dissipate.  This mattress, double size, fits onto an IKEA Ektorp pull-out sofa.  While no one has spent a night on the mattress yet, I've had a few people in my family go lie down on it to try it  out.  Everyone agrees it is comfortable and that the gel in the mattress is great.  A good buy for the money spent.