The Level 4 nipple is suitable for baby's who are 9+ months who prefer a quicker flow rate. Just like the other level nipples from Dr. Brown's, these nipples are shaped to resemble the breast, thereby better promoting a proper latch. Designed alongside medical professionals, the correctly contoured nipple shape and high-grade, soft silicone offer a more comfortable feeding experience and help to avoid nipple confusion. Perfect for switching from breast to bottle and back again! Together with the anti-colic internal vent system, the Level 4 Wide-Neck Nipple gives baby vacuum-free feeding that is clinically proven to reduce colic, decreases spit-up, burping, and gas, better preserves nutrients, and aids in digestion for a good night's sleep. While our bottle works best with the vent system, it's great to have options when baby's feeding develops. Just remove the vent and the feeding experience is similar to most nipple-vented bottles. Fits Dr. Brown's Options+ Wide-Neck bottles. Dishwasher (top rack) and sterilizer safe. BPA free.