The Natural Response teat follows your baby's natural drinking rhythm, allowing you to combine breastfeeding and bottle feeding. The teat has a unique opening that only releases milk when the baby is actively drinking. So when the baby takes a break to swallow and breathe, the milk supply is also interrupted. The wide, soft and flexible teat is designed to mimic the shape and feel of a breast, helping baby to suck and drink comfortably. The anti-colic valve is designed to keep air away from baby's tummy during feeding, preventing colic and discomfort. Philips Avent Natural Response bottles and teats are made of BPA-free* material. In addition, all Natural Response teats are made of soft silicone.