I’m giving it a 5 but I have only slept on it for two nights. When I opened wrapping  there was a very strong Oder. It only took 3 hours for it to fill out. Later that evening my daughters made my bed and put this on top of mattress, the smell was gone by then. I have terrible back problems and I bought a new mattress which is very nice but hard as a brick. I saw these mattress toppers and thought this might make a difference and hopefully it will.  The topper is really comfortable, I can only hope it will help.