The Non-Drip™ Dual Surface Nipple provides your baby with the ultimate in comfort and function by combining a soft surface for feeding with a firmer dimpled surface for teething. The top of the nipple is made of soft silicone, and features a Non-Drip™ valve that allows the baby to control the amount of fluid. And because the valve only opens when the baby is feeding, moms don't have to worry about those pesky leaks. The base of the nipple is made of a firm silicone with raised offset surfaces that are great for a teething. In addition, the Non-Drip™ Dual Surface Nipple features anti-colic vents along the base which help prevent a vacuum from forming in the bottle. This reduces the amount of air the baby ingests, and thus, reduces gas and the chances of colic.