Our anti-colic valve is designed to keep air away from your baby's tummy to reduce colic and discomfort. As your baby feeds, the valve integrated into the teat flexes to allow air into the bottle to prevent vacuum build up and vents it towards the back of the bottle. It keeps air in the bottle and away from baby’s tummy to help reduce colic and discomfort. Philips Avent Anti-colic bottle reduces fussing. Babies fed with Philips Avent Anti-colic bottles experienced 60% less fussing at night, than babies fed with a competitor’s anti-colic bottle.