Natural feeding teat makes it easy to combine breast and bottle feeding Anti-colic valve with twin valve design Ergonomic shape makes it easy to hold and grip the bottle for maximum comfort Made from BPA-free materials The Philips Avent Classic Feeding Bottle is designed to work with baby's natural feeding rhythm. The teat helps baby to control milk as they would do at the breast, making it easy to feed with a bottle only, or combine bottle and breastfeeding. Philips Avent bottles are clinically proven to reduce painful colic and discomfort after feeding. The two piece anti-colic system consists of the AVENT Teat and adapter ring. As baby feeds, the unique skirt on the AVENT teat flexes to allow air into the bottle instead of baby's tummy. Five different teat flow rates are available.