The Natural Response nipple adapts to your baby's natural feeding rate, making it easy to combine breastfeeding and bottle feeding. The nipple has a unique vent that releases milk only when baby drinks, so when baby stops swallowing and breathing, the milk flow stops too. The wide, soft and flexible nipple is specially designed to mimic the shape and feel of a woman's breast, making it easier for your baby to latch on and feel comfortable. The anti-colic valve is specially designed to keep air out of baby's tummy during feeding, helping to reduce colic and discomfort