Serta Perfect Balance Deluxe Organic Crib Mattress Pad 52" x 28" has a 100% Organic cotton quilted top for extra comfort and softness for baby. The 100% waterproof underside protects mattress from liquids. The generous elasticized corners provide a snug fit on most standard size crib mattresses to prevent shifting and sliding. Serta Perfect Sleeper Deluxe Organic Crib Mattress Pad.