The Cotton Flannel Waterproof Mattress Protector by Big Sleep is filled with premium natural cotton filling which is ideal for people wanting to add the natural properties of cotton to their bed. It is ideal for Hot Sleepers or people living in warmer climates. Also, great to be used with Latex or Memory Foam Mattresses to give you that extra layer of healthy breathable cotton. Cotton Flannel top with waterproof base, this product is finished with a fitted skirt.