Natural Newborn Nipple is designed to make it easy to combine breast and bottle feeding. The wide, breast-shape and unique comfort petals make the nipple softer and more flexible to promote natural latch-on. The petals also reinforce the shape of the nipple to prevent it from collapsing in baby's mouth so your baby can feed contently and without interruption. The nipple's shape encourages the same tongue movements suckling babies use when breastfeeding, so transition between the two is less confusing for your baby. The Newborn Nipple is designed for the youngest babies, featuring 1 hole to offer the slowest flow rate. The Natural nipple features twin anti-colic valves that work to make feeding more comfortable for babies. During feeding, the valves release air back into the bottle rather than into your baby's tummy, which reduces colic and discomfort. These nipples are made of soft, durable silicone, which is odorless and flavorless. The nipples can be sterilized in any Philips AVENT steam sterilizer, boiled for five minutes, or washed in the dishwasher.