The unique anti-colic venting system on our Advanced anti-colic bottle draws air away from milk, meaning 80% fewer colic symptoms such as wind, reflux and fussing. Specially designed to reduce colic symptoms for less wind, less reflux and less discomfort Unique anti-colic venting system draws air away from milk, using the venting wheel, venting tube with heat sensing strip and the star valve. Venting tube with heat sensing strip turns pink when baby's feed is too hot Award-winning breast-like teat for natural latch and guaranteed acceptance 3 way, easy-hold bottle with anti-colic slow-flow teat for newborn babies Always BPA and phthalate-free for ultimate reassurance Advanced anti-colic bottles are only compatible with Advanced anti-colic teats and will NOT work with Closer to Nature teats.