Glass bottle does not absorb odor, color or taste (bpa and pvc free);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;Silicone sleeve reduces slips and breakings;Includes stage 2 medium flow nipple for 3 plus months