Unique anti-colic valve: The two piece anti-colic system consists of the AVENT Teat and adapter ring. The adapter ring is an essential part of the bottle design and must always be used. As your baby feeds, the unique skirt on the AVENT Teat ?exes to allow air into the bottle instead of your baby's tummy.Supports breastfeeding: Soft, naturally shaped silicone teat to combine breast and bottle feeding.0% BPA (Bisphenol A): These bottles are made from PP (Polypropylene) - a BPA-Free material.260ml Feeding Bottle Twin Pack contains extra soft Slow Flow AVENT Teats. Ideal when progressing from the 125ml Feeding Bottle.