Sleep and nutrition are vital to your baby"s health and happiness. Clinical studies show that the AVENT bottle significantly reduces fussing, especially at night, and colic in infants 2 weeks of age versus feeding with a conventional bottle. Unsettled and irritable behavior, known as fussing, is by far the most commonly known crying behavior. The two piece anti-colic system consists of the AVENT nipple and adapter ring. As your baby feeds from the bottle, the unique skirt on the AVENT nipple flexes to allow air into the bottle to prevent vacuum build up. Air bubbles move away from the nipple and into the bottle instead of your baby"s tummy. The soft, naturally shaped nipple promotes proper latch-on and allows your baby to control the milk flow making it easier to combine breast and bottle feeding. Nipples are available in various flow rates to allow for your growing baby"s needs. This AVENT bottle is made from PP (Polypropylene) – a BPA-Free material.