The Similac SimplySmart Level 1 Nipple was designed by experts in infant nutrition. The naturally shaped nipple is designed for feeding between breast and bottle. Similac SimplySmart Level 1 Nipples, BPA Free: Includes two Level 1 slow flow nipples. It"s made of silicone. Works exclusively with the Similac SimplySmart system. Recommended for babies from 0-3 months old. Intellivent venting system reduces baby"s excess air intake for less fussiness and gas. The Similac SimplySmart Level 1 Nipple was designed by experts in infant nutrition. The naturally shaped nipple is designed for feeding between breast and bottle. Similac SimplySmart Level 1 Nipples, BPA Free: ?Includes two Level 1 slow flow nipples