The dummy's natural response is to release milk only when the baby is actively drinking. Babies can drink, swallow and breathe using their natural rhythm, just like when breastfeeding. It is therefore easy to combine breastfeeding with bottle feeding. The dummy releases milk when your baby is actively drinking The Natural Response dummy adjusts to your baby's natural feeding rhythm and therefore allows you to easily combine breastfeeding with feeding from a bottle. The dummy has a unique hole that only releases milk when your baby is actively drinking. Therefore, when the baby pauses to swallow and breathe, the milk supply stops. Designed to reduce colic and discomfort The anti-colic valve is designed to prevent air from entering the baby's tummy during feeding and reduce colic and discomfort. Glass is pharmaceutical quality, clean and heat resistant The Philips Avent glass bottle is made from the highest quality borosilicate glass which is heat and heat resistant. It can be placed in the fridge while still warm and is suitable for sterilization. Easy to use and clean and quick to assemble The wide neck makes the bottle easy to fill and clean. Only a few parts for quick and easy assembly. The Natural Response nipples as well as the bottles are BPA free.