These breathable muslin aden + anais Planes Sleeping Bag in size Medium do away with loose blankets for a comfortable, peaceful night"s sleep for baby and you. Made from soft cotton muslin, it allows airflow through the fabric to help prevent overheating and are sized just right to fit over pajamas. 100% cotton muslin. Size small is designed for up to 6 months, 23" - 28" H and 10 - 18 pounds. Size medium is designed for 6 - 12 months, 26" - 31" H and 15 - 24 pounds. Machine wash.