Nipple lets milk flow when baby is actively drinking The Natural Response teat adapts to your baby's natural feeding rhythm, making it easier to switch between breast and bottle. The teat has a unique opening that lets milk flow only when baby is actively drinking. So when they stop to swallow and breathe, the milk stops too. Natural breastfeeding with teat imitating the shape of the breast The large, soft and flexible nipple is designed to simulate the shape and feel of a breast, allowing baby to suckle and feed comfortably. Designed to reduce colic and discomfort The anti-colic valve is designed to prevent air from entering your baby's stomach while breastfeeding, helping to reduce the risk of colic and discomfort. Leak-proof design of the teat helps prevent spillage and loss of milk The opening of the teat is designed to let the milk flow only when baby is drinking. So you can avoid milk loss with peace of mind, whether you're at home or on the go. Pharmaceutical grade glass, purity and heat resistance Made of premium borosilicate glass, the Philips Avent glass bottle is heat and thermal shock resistant. You can therefore place it in the refrigerator, heat it and sterilize it. Easy to use, easy to clean and quick to assemble The bottle's wide neck makes it easy to fill and clean. The bottle has only a few parts for quick and easy assembly. Features: -3 bottles -8oz -flow level 3 -1 months and + -Philips Avent Natural bottles and teats are made with BPA-free materials