WHY DR BROWN'S? The Dr. Brown's Natural Flow baby bottle is the only baby bottle that features a patented internal vent system. This vent eliminates the air bubbles and vacuum effect to allow positive-pressure feeding with no air - similar to breast-feeding. And all Dr. Brown's Natural Flow baby bottles include the following features: Easy to clean and top-rack dishwasher safe - Connects directly to most breast pumps (Standard bottles only) ADDITIONAL TEATS AVAILABLE IN ALL SIZES