With micro air vents help prevent nipple collapse. Elite system with wide nipple and easy-to-hold pediatric angled bottle. The Evenflo Elite nipple has a more natural shape, just like breastfeeding: Promotes proper latch-on, adjusts to baby's suckling, ease transition between breast and bottle, wide, contoured shape with gentle slope. Check bottom of nipple for EvenPace flow rate. All sensitive response nipples are soft and flexible, adjusting to baby's pressure for the right amount of liquid. Micro air vents allow air to return to the bottle, preventing nipple collapse and keeping air out of baby's tummy. The EvenPace nipple selection system ensures the right flow rate based on baby's age and nutritional needs. Look for sensitive response wide nipples in slow, medium or fast flow rates. 0-3 months: slow flow, 3-6 months: medium flow, 6+months: fast flow. The unique nipple cover features an inner wall that forms a barrier to help keep the nipple clean.