Philips Avent Silicone Teats Airflex 4 Holes 2pcs - SCF634/27-plastic2 pcs Fast flow teat 6m+ Anti colic valve proven to reduce colic* 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 babys tummy to help reduce colic and discomfort. 60% less fussing at night*