The Dr. Brown's Baby Bottle Bundle includes 6 slow flow Level 1 silicone nipples specially designed for newborns and 2 replacement vent kits compatible with Dr. Brown's Options+ narrow baby bottles. The Level 1 nipples feature an anti-colic internal vent system clinically proven to reduce colic, spit-up, burping and gas. The vent system creates a vacuum-free feeding experience closest to breastfeeding by allowing air into the bottle while preventing the nipple from collapsing. This enables the nipples to provide a slow, consistent flow rate so babies can feed comfortably at their own pace. The breast-like nipple shape encourages proper latching to ease the transition between breast and bottle feeding. Made from super soft 100% silicone, the Level 1 nipples fit all Dr. Brown's narrow neck bottles. The nipples and vent system help preserve nutrients and aid digestion for better sleep. The replacement vent kits allow you to swap out any worn or lost parts from the Options+ bottles. Each kit contains 2 vent inserts, 2 reservoirs and 2 travel discs compatible with 8oz/250mL Options+ narrow bottles. The bundles' nipples and vent kits are top-rack dishwasher safe and BPA free.