Your options have never been better with Dr. Browns Natural Flow Anti-Colic Wide Neck Baby Bottles. The anti-colic internal vent system is clinically proven to reduce colic. Dr. Browns bottles provide a more comfortable feeding experience for baby by decreasing spit-up, burping and gas. 5oz Anti-Colic baby bottles The anti-colic vent system is proven to help preserve bottle milk nutrients and aids in digestion for a better sleep. Dr. Brown s Natural Flow Anti-Colic baby bottle works best with the internal vent system in place but can be removed as baby s feeding develops – no need to introduce a different bottle. Safe for use in dishwasher (top rack only), electric and microwave sterilizers or boiling water. These are used but have been sterilized. No nipples. Please note, these are not the new Options+ bottles