Im used to a 4 memory foam topper.  I bought this to go on a new mattress that was too hard because the 4 would have made the bed too high. I still had trouble sleeping, even with the memory foam. But that is just me. My other one was like sleeping on a marshmallow, so there was quite a bit of difference in the comfort level for me. It probably would have been fine on a mattress that was softer.