I do not like "Memory Foam" as it compresses and is hot and makes changing positions a feat. This polyurethane mattress supports the entire body without making you feel like you are being submerged. It is cool, soft and the 4-inch thickness guarantees that I will not be feeling the mattress beneath but the straight level of the bed, of course, is maintained.. so my back is straight at all times. I put a mattress pad on top of the foam topper so that it not only protects the foam but keeps the edges nicely fitted to the edge of the mattress beneath. I had been looking for years for this product and had almost given up hope until I found it on Great Offer Stock. So happy.