Product Description Comotomo Silicone Replacement Nipples feature a wide-mound with built-in air-vents to help even the fussiest babies take a bottle. The naturally shaped design mimics breastfeeding to help make the breast to bottle (and back) transition seamless by mitigating ?nipple confusion? issues. The built-in dual anti-colic vents help to reduce colic and ensure consistent milk flow every feeding. Comotomo nipple packs are replacements specifically designed for Comotomo Baby Bottles. They are available separately in 4 stages: Slow Flow (1 Hole) for ages 0-3 months, Medium Flow (2 Holes) for ages 3-6 months, Fast Flow (3 Holes) for ages 6+ months, and Variable Flow (Y-Cut) for ages 6+ months (thicker fluids). From the Manufacturer Comotomo Nipple-Packs are replacements specifically designed for Comotomo Baby Bottles. Each pack comes with 2 silicone nipples designed to most closely mimic natural breastfeeding. Our naturally shaped, soft, silicone nipples are ideal for babies who have trouble transitioning from nursing to bottle-feeding. Each replacement nipples also have two truly innovative vents that are built in to prevent colic, while totally eliminating leaking issues. ?Truly? Slow Flow (1 Hole) 0-3 months Medium Flow (2 Hole) 3-6 months Fast Flow (3 Hole) 6+ months Variable Flow (Y-Cut) 6+ months (thicker fluids)