Memory foam is made of polyurethane and added chemicals that increase its viscosity and density. Memory foam is firmer when cooler. High density memory foam reacts to body heat-molding to a warm body in a few minutes. Memory sleep pillows custom contour to the head and neck for comfort. Cervical pillows provide therapeutic neck support by conforming to and properly aligning you head and neck with your spine. They will give optimum support of the natural curve of the spine. Travel pillows cradle your neck to relieve pressure, prevent stiffness and alleviate soreness while traveling by plane, train or automobile. It is lightweight and fits easily into a carry-on bag or back pack.