"The memory foam filling and synthetic fiber exterior let air pass through for superior breathability. The pillow is large and was cumbersome to carry, especially for light packers. It can get hot and stuffy on an airplane, so the synthetic materials used to create this Sleep Number travel pillow are light and airy. The memory foam filling is bouncy and lightweight, and the soft fabric pillowcase is cooling enough to prevent overheating while sleeping in a plane, car, or train." - Travel + Leisure Editors