Philips Avent Natural Baby Bottle set includes four 9 oz (260 ml) bottles designed to mimic the natural feel of breastfeeding. These bottles feature the Natural Response nipple, which allows babies to control the pace of feeding by drinking, swallowing, and breathing at their own rhythm. The no-drip nipple design helps prevent leaks, while the integrated anti-colic valve is engineered to reduce colic and discomfort by keeping air away from the baby's tummy. Suitable for infants aged 3-6 months, these BPA-free bottles come with Flow 3 medium-response nipples.