MAM's nipples are designed to resemble a mother's nipple during breastfeeding. To achieve this, MAM observed 16 infants breastfeeding using ultrasound technology. The result is a unique, flat shaped nipple that fits perfectly in baby's mouth and makes the switch back-and-forth between breast and bottle easy. All MAM products are made from BPA-free materials for maximum safety. These nipples fit all MAM bottles and are suitable for both breast milk and formula. The MAM nipple is available in five different flow rates: 0 - extra slow flow (newborn), 1 - slow flow (0+ months), 2 - medium flow (2+ months), 3 - fast flow (4+ months), and x - extra fast flow for thicker liquids (6+ months). ** Market research 2009-2020, tested with 1,572 babies .