Dr. Brown's Natural Flow bottle is an award-winning, clinically tested bottle designed to reduce colic, gas, and discomfort. Made from a combination of high-quality polypropylene and soft 100% silicone, these bottles feature an innovative internal vent system that helps reduce spit-up, burping, and gas while preserving the nutrients in breast milk and formula. The bottles come with a set of three Level 1 silicone nipples, ideal for newborns and babies beginning bottle feeding, providing a smooth and consistent flow. Plus, three patented two-piece internal vents and a cleaning brush. Each nipple is carefully designed to ensure a smooth and predictable flow, helping your baby latch on naturally and comfortably, just like breastfeeding. Safe, convenient, and versatile, these bottles are dishwasher and sterilizer safe, making cleanup a breeze. They are also BPA-free and designed to fit most breast pumps, offering maximum convenience for busy parents.