Converts the original Dr. Brown's 8oz bottle into a Dr. Brown's Options 8oz bottle;Removable when baby's feeding becomes more developed;Use vent system to create a fully vented bottle;Vent system keeps air from entering milk and baby from getting gassy;Vent system helps retain vitamins in milk;Vent system reduces gas in baby and maintains higher levels of vitamins in milk;Includes 1 vent insert, 1 vent reservoir, 1 cap and 1 collar;Bpa free and made in USA