These are much thinner than 4", barely 2.5". Never fully expanded, even after four days. Even if it did, it doesn't look like it would be as thick and comfortable as a 4" folding mattress we bought from Modway brand and were happy with years ago. I'm going to try to return and find ones from Modway. I also don't like that it's listed as a mattress, but when you get the package it says 'mattress topper'. I'm sure that's just a formality, but which is it? Mattress means it can stand on its own. Mattress topper means you put it on top of another mattress. Feels like false advertising.