Ultra-premium PPSU material will not absorb odor or color and stands up to repeated sterilization;The 1-piece Clean Flow vent is easy to clean, it prevents leaks, reduces colic and provides a consistent liquid flow;Unique nipple design prevents nipple collapse, promotes proper latching and allows for easy breast-to-bottle and bottle-to-breast transitions;Includes Stage 2 Medium Flow Nipple for 3+ months;BPA, PVC, phthalate and lead free