The Zero gravity Medical Latex is our softest of the Collection. Lying on this mattress will make you feel like you're in suspended animation. The very top layer is comprised of 2" of 19ILD Talalay Latex: soft enough to be comfortable but strong enough to keep your body straight. The middle, transitional layer is comprised of 2" of our Zero Gravity Serene Airflow foam. This is a medical grade foam used to make mattresses for people with fybromyalgia, hip replacement surgeries and severe arthritis. It's also used in the medical industry to make mattresses designed to alliviate bed-sores. This is a great mattress for side-sleeps or for those who want a soft surface.