The 4-5 inch thick natural rubber molded pillow molds to your neck for superior comfort and still breathes and ventilates well. It is very flexible as well. The cover is fancy European Organic Cotton Or NEW Organic Cotton Knit outer. The pillows use the best rubber with high purity standards. No vanillin (a petroleum based product which contains dimethyl sulfate and is highly toxic according to a Virginia University study.) or other perfumed scent is present in your organic rubber pillow. Pure Rest uses only Dunlop rubber rather than Talalay for this reason.