Variflo Variable Flow 3m+ Nipples. 0% BPA-free. Soft nipple. Silicone nipple. BPA-Free nipple allows your baby to control milk flow more like breastfeeding which can help reduce overeating and spit-up. A unique skirt system flexes to allow air into the bottle and promotes healthy active feeding and reduces colic. . Reduces colic. . A clinical trial demonstrated that at 2 weeks of age babies fed with the AVENT Bottle experienced less colic than babies fed with a conventional bottle. . Allows air into the bottle instead of your baby's tummy. . As your baby feeds the unique skirt on the AVENT Nipple flexes to allow air into the bottle instead of your baby's tummy. Like natural breastfeeding your baby controls the milk flow. . Variable flow nipple for thicker feeds. . The variable flow nipples has a slot cut which provides an adjustable for the flow rate. Flow rate can be varied by simply turning the bottle to align the I II or III markings on the nipple with the baby's nose.