97% Rayon made from Bamboo, 3% Spandex Breathable material Designed for sensitive skin Comfortable stretch Kyte BABY knotted caps are made from silky smooth bamboo rayon allowing them to fit comfortably on your baby's head while being the right amount of tight. They also coordinate well with all of our layette and sleep bags so you can mix and match. Babies are constantly growing, so our incredibly stretchy material is excellent for creating knotted caps as the stretch is able to fit a wide range of head circumferences comfortably. The cooling and softness of our bamboo rayon fabric is also perfect for your newborn baby's delicate skin.According to the National Center for Health Statistics, an infant in the 3rd percentile has a head circumference of 31.49 centimeter making our newborn size a great choice for newborns including premature or smaller babies. For those babies in the 97th percentile whose head circumference is 38.85 centimeter our 0-3 month’s size will be a great fit.Kyte BABY hat measurements:Newborn: 11 inch/28 centimeter (fits head circumference of 11.5-14 inch/30-36 centimeter)0-3 months: 12.5 inch/32 centimeter (fits head circumference of 13-15.5 inch/34-40 centimeter)3-6 months: 14 inch/36 centimeter (fits head circumference 14.5-17 inch/38-44 centimeter)6-12 months: 15.5 inch/40 centimeter (fits head circumference 16.5-19 inch/42-48 centimeter).Our products are ethically and responsibly made with bamboo, one of the most sustainable resources in the world. This way, we are able to produce the softest products. The soft, breathable and smooth bamboo-based fabric gives your kids the comfort they need.