100% Cotton 100% cotton. Swaddling has been around for ages as it helps to prevent the startle reflex. But forcing the baby??s arms to their sides or over their chest prevents two natural behaviors that frustrate the baby and they fight to get their hands free. The dual zipper makes diaper changing a breeze and eliminates the need to remove the swaddle and having to completely re-swaddle the baby. The patented design eliminates any risk of loose fabric and the zipper replaces noisy Velcro or bothersome snaps. The unique wing design not only prevents baby’s nails from scratching face, but also allows the baby to both sleep with their arms in their preferred arms up position and gives enough movement. 2 CONVENIENT SIZES: You can purchase the Small size Swaddle Bag for 0?C3 months newborns and Large size for 3?C8 months older infants.