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 nipple also has two truly innovative vents that are built in to prevent colic while totally eliminating leaking issues. Comotomo Replacement Nipples grow with your baby and are available separately in 4 stages: truly Slow Flow (1 Hole) for ages birth-3 months Medium Flow (2 Hole) for ages 3-6 months Fast Flow (3 Hole) for ages 6+ months and Variable Flow (Y-Cut) for ages 6+ months (thicker fluids).