The teat works with the baby's natural feeding rhythm. Your baby controls milk flow more like breastfeeding, which can help reduce over eating and spit-up. A unique skirt system, with a built-in one-way air valve at its base, flexes to allow air into the bottle to prevent a vacuum, whilst milk flows at a rate the baby can control. This promotes healthy, active feeding and reduces colic. You may hear the valve quietly working away, but watch as the bubbles move away from the teat - that's your guarantee that air is going into the bottle, not into your baby's tummy. The naturally shaped teat promotes proper latch-on and makes it easier to combine breast and bottle feeding. Learn more about how the AVENT Feeding Bottle works.