Upon receiving the mattress topper, I followed the directions for opening it. I unrolled it and let it set for 48 hours. It regained its shape and filled out nicely. It fit well on the queen size mattress in my guest bedroom. This mattress is older and losing some of its support. With this topper, it is much firmer now and will provide a better night’s sleep. This is a nice alternative to buying a new mattress.