Works like breast¹: the teat releases milk when your baby drinks, which is different from the traditional free-flow teats; as with breastfeeding, it can take time for baby to get used to this Works like the breast: The teat releases milk when baby actively drinks, this is different from the traditional free-flow teats. As with breastfeeding, it can take time for a baby to get used to this. The unique Natural Response teat opening only releases milk when the baby actively drinks, when pausing to swallow and breathe, no milk flows; the no-drip teat design prevents spills and lost milk Right teat flow: find your baby's perfect flow rate and personalise your Avent bottle; age is a guide, but your baby's approach will help determine when to move to a higher or lower teat flow rate 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 Easy to clean: the wide bottleneck makes filling and cleaning effortless; only a few parts for quick and simple assembly The set includes: 2x 8oz Natural Response glass baby bottles with medium flow teats (Flow 3)