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. Available 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). Sold separately.