The main advantage of Dr. Brown's bottles is that your baby will not swallow air thanks to the patented internal ventilation system. Do you know how it works? The air enters through the holes in the upper valve and passes through the internal ventilation tube to the bottom of the bottle without mixing with the milk. This internal functioning reduces colic, gas, burping and vomiting from reflux. Dr. Brown's bottle maintains vitamins A, C and E and lipids in milk, whether breast or formula milk, for longer, minimizing their oxidation. Prevents the accumulation of fluid in the middle ear, reducing the risk of otitis media. Dr. Brown's baby bottles are BPA free and do not contain PVC, Phthalates or lead. 100% Silicone Teat