The Phillips AVENT BPA Free Adaptor Ring is for use with the AVENT polypropylene bottle as part of the two piece anti-colic system. The Phillips AVENT BPA Free Adaptor Ring features: * The two-piece anti-colic system consists of the AVENT Nipple and Adapter Ring * As your baby feeds, the unique skirt on the AVENT Nipple flexes to allow air into the bottle instead of your baby"s tummy * Includes 3 Adapter Rings * All AVENT pacifiers are 100% BPA free