Dr. Brown's Options: The market's first convertible bottle that can be used with or without the vent system. The new vent system is designed to grow with baby, and dr brown recommend using this system to experience all the health benefits of our bottle. It helps reduce feeding problems, helps digestion and helps preserve vitamins. Some moms and dads find removing the vent a convenient option as their baby's feeding becomes more developed. The nipple venting creates a paced flow, and provides a feeding experience similar to most nipple-vented bottles. Options bottles fit most breast pumps, and are BPA-free.