The Philips Avent Glass Natural bottle with the Natural Response nipple lets baby control the pace of the milk, like they do when breastfeeding. The nipple's unique opening and tip only releases milk when your baby actively drinks. When baby pauses to swallow and breathe, no milk flows. Baby can drink, swallow, and breathe using their natural rhythm, just like they do when breastfeeding. This bottle easily combines 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. This Natural Philips Avent bottle is made of premium quality borosilicate glass, a BPA-free material. It is heat and thermal shock-resistant, so it can be safely stored in the fridge, warmed and is easy to wash and sterilize. The Natural Response nipples come in flow rates 1-5, to keep up with your baby's growth. Philips Avent recommends using the Philips Avent Natural baby bottle with Philips Avent Natural bottle nipples.