Wow, what a difference.  We were sleeping on a 6 inch split queen futon mattress.  The 4 inch plush memory foam topper is just right to add needed support.  We were able to cut it to fit our 30 inch wide mattresses and it works with adjustable raised bed and heated mattress pad.  So much more comfortable. I'm sensitive to chemicals but this has no odor and was ready within hours although we waited 48 hours as suggested.