The Philips Avent Glass Natural bottle comes with a Natural Response nipple that allows babies to control the flow of milk similar to breastfeeding. This baby bottle is made of high-quality borosilicate glass, a BPA free material that is resistant to heat and thermal shock, making it safe for fridge storage and warming, as well as easy to clean and sterilize. It features a wide breast-shaped nipple with a soft texture that makes it easy to switch between breast and bottle feeding. The no-drip nipple design prevents milk from leaking and comes in Flow 2. Additionally, the anti-colic valve reduces discomfort by directing air away from the baby's tummy. The box includes four 4oz Natural Glass bottles with Flow 2 Natural Response nipples.