Innovative natural-flow bottles are designed with a patented internal vent system meant to prevent air bubbles and the resulting feeding problems including burping and gas, while helping to maintain essential vitamins in the milk. The top-rack dishwasher-safe design ensures fuss-free cleaning, while the vent-free option provides added convenience as baby develops. Style Name:Dr. Brown's 3-Pack Bottles. Style Number: 5321559. Available in stores.