Made from BPA FREE durable, break-resistant plastic. Can be boiled; top rack dishwasher safe; microwave steam sterilizer safe. Graduated in both ounces and ml. An anti-colic nipple helps to prevent ingestion of air by baby, which may cause colic. Nûby™ has taken this one step further by adding the Nûby™ nipple with raised offset surfaces that assist in the eruption of gums. The Medium Flow nipple is perfect for babies aged 3-6 months.