Mattress toppers are esigned to lie atop an existing mattress. They are made primarily from foam. Their function is to provide a layer of comfort and warmth between the user and the mattress. They are of particular benefit when the existing mattress is worn or uncomfortable. Toppers quite often have a contoured profile to facilitate airflow. Visco-elastic foam toppers are regularly used in medical institutions because of their pressure relieving properties. The foam used in the construction of these memory foam toppers reacts to both pressure and temperature. This combined with its greater density are properties that give them their characteristic "weightlessness" sensation.