Colic in infants may be caused by a combination of in?uences including ingesting air during feeding. The new advanced comfort? range from closer to nature is specially designed to help reduce air bubbles in the milk and to encourage a good latch-on to help reduce the risk of baby ingesting air during feeding. The air vents down through the tube and into the air-space at the base of the bottle, completely bypassing the milk. Closer to Nature advanced comfort? Bottles provide optimum venting during feeding via a unique tube and valve system. They also help provide a continual feeding action via an easy-latch-on teat. The breast like shape of the Closer to Nature teat allows baby to latch on easily and further supports the transition between bottle and breast. Flex and stretch ripples allow the Closer to Nature teat to mimic the natural flex and movement of mum?s breast. Designed to be held in the most natural position during feeding, the compact shape of Closer to Nature bottles allows baby to be closer to you. For total reassurance, all of our products are free from Bisphenol A (BPA).