Each package includes four natural silicone nipples designed for babies 3+ months. The Medium Flow Stage 2 nipples are ideal as your baby's feeding needs evolve from newborn stage. Micro Air Vents allow air to return to the bottle, preventing nipple collapse and keeping air out of baby's tummy. Sensitive Response technology makes these nipples soft and flexible, adjusting to your baby's natural suckling pressure for consistent, comfortable feeding. These nipples are dishwasher safe (top rack only) for easy cleaning. Wash and sterilize all parts thoroughly after each use. Made in Mexico with quality you can trust. Choose medium flow if your baby appears to be sucking too hard on slower nipples or shows signs of frustration during feeding. The nipple hole size is right when milk flows steadily without sputtering or gulping.