The Natural Response dummy only gives milk when the baby drinks. This allows your baby to drink, swallow and breathe at a natural pace, just like breastfeeding. It makes it easy to combine breastfeeding with bottle feeding Anti-colic valve prevents air from getting into baby's tummy when breastfeeding to prevent colic and discomfort. The wide, soft and flexible nipple recreates the shape of the breast to give your baby a comfortable feeding experience. The Natural Response nipple conforms to your baby's natural drinking rhythm and therefore allows breastfeeding and bottle-feeding to be easily combined. This nipple has a valve which ensures that milk only flows when your baby has begun to drink. The flow stops when the baby decides to take a break to drink the formula and breathe. All babies require a special approach when feeding and keep at their own pace. We have developed nipples with different flow rates so you can find the best option for your baby. All Natural Response nipples are made of soft silicone. The nipple has a special valve to ensure that the milk only flows when your baby has begun to drink. This prevents your baby from spilling milk in the home or outdoors. The bottle is easy to wash and fill, thanks to its wide neck. Fewer parts allow the bottle to be assembled and disassembled quickly. The Philips Avent Natural series bottle is made from BPA-free* material. The Philips Avent premium borosilicate glass bottle withstands changing temperatures, so it can be safely stored in the fridge, heated, and sterilized. Our new Natural Response bottles are different to those without a valve. As with breastfeeding, it may take you a few days to adjust to it. This is normal.