I purchased this mattress mainly because the dimensions given allowed for it to fit in the daybed trundle. It actually might be even a little thicker than listed because I could just get it pushed in. It will not be able to be made up and pushed under but maybe it will with just with the fitted sheet. That being said I am thrilled with this purchase. When I first removed the packaging I was a little upset due to thinking it was going to be a very thin mattress. But after a few hours it is like it bloomed. And as stated above it just fits now. I laid down on it for about ten minutes and I must say that I could not tell that I was laying on a trundle bed. It was so very comfortable. I definitely recommend this mattress if you are in the market for a thinner mattress. Very happy with this purchase.