The Philips Avent Natural Response nipple by Fratelli only releases milk when the baby actively drinks. Babies can therefore drink, swallow, and breathe using their natural rhythm, like on the breast – making it easy to combine breast and bottle-feeding. The wide, soft, and flexible nipple of the Avent bottle is designed to mimic the shape and feel of a breast, helping the baby to latch on and feed comfortably. The nipple opening is designed to release milk only when the baby is feeding, so you can confidently avoid milk loss, whether at home or on the go. This Natural Response Philips Avent bottles are different from free-flow baby bottles. Just like breastfeeding, it could take a few tries to get it right. That's perfectly natural.