Natural Response nipple supports your baby's natural drinking rhythm: baby controls the pace of the milk flow, just like breastfeeding Designed with a unique opening and tip that only release milk when your baby actively drinks: when pausing to swallow and breathe, no milk flows No-drip nipple design helps prevent lost milk from the tip of the baby bottle, giving you peace of mind; these nipples are slow flow (Flow 2) Anti-colic valve for your and your baby's well-being: it keeps air away from your baby's tummy during feeding to reduce colic and discomfort The set includes: 4x Natural Response nipples, slow flow (Flow 2)