Less Air, More Smiles- The advanced anti-colic bottles uses unique 3 piece anti-colic technology to provide optimum venting during feeding via a unique tube and valve system. Air can enter the bottle safely, vents down through the tube and into the air-space at the base of the bottle, drawing air away from the milk. Award-Winning- Breast-Like Nipple Like a breast because babies prefer it that way. Heat Sensing Tube The anti-colic tube changes color if the milk is too hot. Simply sip the tube for 5 seconds to see the feed temperature. Pink indicates the temperature is too hot. No Leak Promise The star valve at the base of the anti-colic straw keeps milk from traveling up the tube meaning 80% less gas, spit-up and fussing and 100% more smiles.