Philips Avent Glass Natural bottle with the Natural Response nipple lets baby control the pace of the milk, like they do when breastfeeding. The nipples' unique opening and tip only releases milk when your baby actively drinks. When pausing to swallow and breathe no milk flows. Baby can drink, swallow, and breathe using their natural rhythm, just like they do when breastfeeding. Easily combine breast and bottle feeding with a wide breast-shaped nipple with a soft feel that mimics the shape and feel of a breast plus baby controlling the flow of milk like they do when breastfeeding. The nipple has a no-drip design which helps prevent lost milk from the tip. An anti-colic valve integrated into the nipple is designed to reduce colic and discomfort by sending air away from your baby's tummy. The ergonomic shape makes it comfortable for parents to hold. Assembly is simple with only a few parts and the wide bottle neck makes filling and cleaning easy.