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 teeth by gently massaging infant’s gums. The first and only Non-Drip™ nipple is uniquely designed to prevent drips and spills. With a pressure sensitive valve feature safely built right into the nipple, fluid only flows out of nipple with sucking actions of baby. This special valve closes when sucking action ceases, ensuring a leak-resistant bottle.