The Dr. Brown's Natural Flow Wide-Neck Baby Bottles offer a wonderful feeding experience with innovative vent technology. Dr Brown's bottles use a patented 2-piece internal vent system for your baby's comfort. This system creates positive-pressure flow for vacuum-free feeding that is similar to breastfeeding. Dr. Brown's bottles are completely BPA, PVC, lead and phthalate free for your baby's safety. Each bottle comes with 1 Level-One silicone nipple, 1 two-piece patented internal vent system, 1 cleaning brush and instructions.