Dr. Brown has options. 5 ounce wide-neck glass bottles, 2 pieces. We advise utilizing the anti-colic vent system because it is designed to grow with the child in order to reap the maximum health benefits of our bottle. It enhances digestion, minimizes troubles with eating, and protects vitamins. Some parents decide to remove the vent as their baby's feeding abilities advance. Because of the timed flow produced by the nipple venting, the feeding experience is comparable to that of most nipple-vented bottles.