The Dr. Brown's baby bottle bundle includes 4 narrow 4 oz anti-colic bottles with level 1 slow flow nipples and a 3-pack of narrow travel caps. The anti-colic bottles feature an internal vent system clinically proven to reduce colic by decreasing spit-up, burping and gas. The vacuum-free feeding experience mimics breastfeeding, with a consistent flow rate so baby can feed at their own pace. The vent system also helps preserve nutrients and aids digestion. The breast-like nipple shape encourages proper latching and eases switching between breast and bottle. As baby grows, the internal vent can be removed without introducing a new bottle. The BPA-free narrow bottles are designed to nourish through all feeding stages and are recyclable and dishwasher-safe. For every Dr. Brown’s bottle purchased, one ocean plastic bottle is prevented through their Plastic Bank collaboration. The included narrow travel caps securely seal the bottles for transporting formula or breastmilk. They are reusable, dishwasher-safe and BPA-free. The bottles and caps complement each other perfectly - the anti-colic bottles provide the most comfortable feeding experience, while the caps let you take that experience anywhere.