The new Breast Size Nipples are designed to make breast-feeding and bottle feeding work better together. By mimicking the natural shape, feel, and function of a mother’s breast, the Breast Size Nipples help to ease the transition from breast-feeding to bottle feeding. They feature a soft natural shape that gently flexes and elongates, allowing the baby to easily position the nipple at the correct angle for feeding. In addition, the Breast Size Nipples also feature valves in the base of the nipple which help prevent colic, and soft nubs on the nipple’s surface to massage a soothe sore gums. * Works with all Nûby™ Natural Touch™ bottles.