Avent Natural Response 2 Baby Bottles 125ml 0 Months and + are bottles with a flow 2 nipple, designed to reduce colic and discomfort. The Natural Response teat adapts to baby's natural feeding rhythm, making it easier to alternate between breast and bottle feeding. The teat has a unique opening that allows milk to flow only when baby is actively drinking. This means baby can stop to swallow and breathe, and the flow stops too. This teat is wide, soft and supple to mimic the shape of the breast. The anti-colic valve prevents air from entering baby's stomach during feeding.