A 100% natural cotton surface is a soft knit fabric backed with ultra-thin breathable, waterproof polyurethane membrane. Scientifically researched and lab tested by Quorum Pharmaceuticals, a trusted leader in the field of allergy drugs. Fitted skirt and patented safety “stay on corners” stop the pad from slipping off the mattress. The pad is sized to allow for 1” of shrinkage. Cradel size 18″ x 36″.