Dr. Brown's Original Bottle 4 Ounce ( 4 Pack ) - Brand new in box as shown Brand Dr. Brown's Color Brown Material free PVC Free, BPA Free Item Weight 0.75 Pounds Bottle Nipple Type Slow-flow nipple About this item Vent system eliminates negative pressure and air bubbles to help reduce colic, spit up, burping and gas Fully vented bottle design provides vacuum free feeding similar to breastfeeding Helps maintain vitamins C, A and E plus lipids BPA free Includes 4 ounce bottles Clinically proven to reduce colic Dr. Brown's baby bottles are fully-vented and clinically proven to reduce colic.* Dr. Brown's anti-colic internal vent system helps prevent ingestion of air bubbles and eliminates the vacuum effect which helps reduce spit-up, burping and gas. It also means no nipple collapse or fluid buildup in baby's ear. * Ellett, Examination of the Effect of Dr. Brown’s Natural Flow Baby Bottles on Infant Colic, Gastroenterology Nursing, May/June 2006 Proven to help preserve vitamins A university study set out to measure nutrient levels in baby bottle breastmilk and formula. It was determined that Dr. Brown's fully-vented bottles help preserve levels of important nutrients -- vitamins C, A, and E + lipids. The vent system reduces air bubble oxidation of the milk, which is fragile and susceptible to nutrient loss. Slow-flow nipple for paced feeding Chosen by lactation consultants and recommended by pediatricians,** Dr. Brown's slow-flow rate is ideal for switching between breast and bottle. The internal vent system and silicone nipple work seamlessly together, resulting in controlled flow so babies feed at their own pace. Paced bottle feeding is a way to feed baby that mimics breastfeeding which makes it easier to switch baby from breast to bottle and back again. **QuintilesIMS Health ProVoice Survey, 2018 Fits most breast pumps Dr. Brown's Natural Flow Original bottles attach directly to most breast pumps making it easy to pump and store without having to use extra bottle vessels.