The Dr. Browns Natural Flow Standard Baby Bottles offer a wonderful feeding experience with innovative vent technology. Dr Browns bottles use a patented 2-piece internal vent system for your babys comfort. This system creates positive-pressure flow for vacuum-free feeding that is similar to breastfeeding. The breast milk or formula flows freely without nipple collapse. As the baby feeds, air is channeled from the nipple collar through the vent system to the back of the bottle. Air never mixes with the breast milk or formula so oxidation is prevented, thereby maintaining essential vitamins such as C, A and E. The vent system eliminates air bubbles in the formula or milk, which helps to reduce feeding problems like colic, spit-up, burping and gas. Dr. Browns bottles are completely BPA, PVC, lead and phthalate free for your babys safety. The Newborn Feeding Set comes with 3 8oz/240ml Standard bottles, 2 4oz/120ml Standard bottle, 2 extra Level-Two silicone nipples, 2 Storage/Travel caps and 3 "cleaning" brushes are small nipple brushes and they are INSIDE the bottles. .