I was rather skeptical at first because it came in a tight roll. I would like to warn the buyer that it's not easy to cut it out of the heavy plastic wrapper. My anxiety was at an "8", worried that I'm cut the new mattress. 

The mattress itself was set flat and left alone for a week. Results? It straighten nicely, but it was almost as flat as at the start. There was a little puffing up but not attention grabbing.   I will say that the the washable cover is a wonderful feature. And it seems to hold up to washing. I've now washed it twice.  

I'm not sleeping on this mattress, it's not one that I'd recommend for sleepovers. NOW, I gave a 3-star review because the mattress is ok for my beloved dog who seems to like the limited amount of puffing out.