Made with two layers of jersey organic cotton fabric for maximum comfort and flexibility on top and bottom with an ultra-thin waterproof barrier in the center. Features DrySleep technology, which effectively blocks liquids from passing through to the mattress below. Some water vapor is allowed to escape, which helps provide a more comfortable sleep. Also blocks dust-mites from penetrating the mattress sleeping surface. Versatile design handles mattress depths from 9" to 16" with organic cotton skirt and full elastic perimeter.