Born Free Nipples Stage 3 Twin Pk 2 pack - Level 3 Fast Flow wide neck BornFree? Nipples, recommended for babies of 6 months plus. also operates as a Medium Flow nipple with some thicker types of formula. Born Free uses the highest grade of estrogen free silicone. the nipple structure is made of silicone which helps reduce the chance of the nipple collapse. born free offers a complete line of nipples with different flow levels, depending on desired feeding rate, whcih helps mothers transition from breast feeding to bottle feeding.