Aden + Anais fitted crib sheets are designed with material that allows the bedclothes to breathe, regulating your baby‘s temperature. This is especially helpful in summer months, when the heat can seep into your home during naptime during the day, or on winter nights to help defend against any drafts in baby‘s room and keep him warm and snug. The fitted crib sheets are available in muslin cotton or bamboo muslin. Both materials are smooth to the touch, long lasting, and machine washable. The sheets fit standard crib mattresses.