The Room² waterproof sheet is fitted and designed to protect the Room² mattress so the baby's bassinet stays fresh and clean. This sheet consists of a high quality thread count cotton top, an absorbent, padded layer, a waterproof barrier, and finally a polyester bottom layer with an elasticized fit. The top is fully waterproof, so you never have to worry about spills and stains seeping through to the mattress. Machine wash and dry.