Created by a physician, Dr. Brown's Natural Flow baby bottles feature a patented internal vent system that helps reduce colic, spit-up, burping and gas. The positive pressure design allows babies to feed comfortably, because the vent system eliminates the air bubbles and vacuum. All parts are dishwasher safe. 3 pk Polypropelene bottles plus bonus bottle of Dr. Brown's Standard 8 oz baby bottles, Level-1 silicone nipples and 2 cleaning brushes. BPA FREE.