The SoftFlex™ Natural Nurser™ was 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 baby's transition from breast feeding to bottle feeding becomes easy. Superior anti-colic valves in the base of the nipple help prevent colic, and soft nubs on the surface massage baby’s gums. Additionally, this bottle is made from a high grade of Poly Propelene material which is 100% Bisphenol A FREE and is fully interchangeable with the SoftFlex™ Silicone system.