We got this mattress topper to help out with a new latex mattress that ended up being just a little too firm. This topper is perfect for supporting hips and back for any position of sleep. We didn't realize that it needs at least 48 hours to expand. The wait was torturous for me, as I just wanted to try it out! During the expansion time, we noticed an odor about it. Nothing overly offensive, just noticeable.  Now that it is on our bed, we do not notice the smell at all. It was nice to find the 4" option for such a good price.