The Natural Response Teat releases milk only when baby actively drinks. Babies can drink at their own rhythm like on the breast, so easy to combine breast and bottle feeding. Finding the right teat is important. See more info below. The teat opening is designed to release milk only when the baby is feeding. So you can confidently avoid milk loss whether at home or on the go. Anti-colic valve is designed to keep air away from baby's tummy during feeding, to help reduce colic and discomfort. Avent Natural Baby Bottle Baby Milk Bottle for Newborns+ BPA Free & Anti Collic -SCY903/03 in Clear