Dr. Brown's Polypropylene 8 Oz Bottles are natural flow baby bottles a with level-one nipple. * Polypropylene bottles are BPA Free * Patented internal vent system created by Dr. Craig Brown eliminates the vacuum and air bubbles to help significantly reduce colic, spit-up, burping and gas * Fits all of the existing Dr. Brown's standard nipples * Works with all of the existing Dr. Brown's convenience accessories including microwave sterilizer, drying rack and dishwasher basket * 8-ounce standard size