Questioned the fact that this is a two piece system; they are literally separated, 3.5 inches of cushion and approximately 1.5 inches of memory foam, not sure why. Anyway, we put the two piece system on top of our current mattress system. This caused a significant elevation, but likewise, it sleeps like a cloud. You probably could get away with just using the 1.5 inches of memory foam, especially if you desire more firmness, but since we don't mind the added height or the cushiness were stick with both pieces. All else aside for a little over $****, you cant beat it.