The Natural Response Teat releases milk only when the baby actively drinks. This allows babies to drink at their own rhythm, mimicking breastfeeding and making it easier to combine breast and bottle feeding. The teat features an anti-colic valve designed to keep air away from the baby's tummy during feeding. The unique nipple opening only releases milk when the baby actively drinks, unlike traditional free-flow teats. Finding the right teat flow rate is important for your baby. This bottle-feeding nipple only opens to release milk when the baby is feeding.