All Dr Brown's teats are super-soft and made of high-grade silicone. Dr Brown's teats are precision cut to allow for the maximum performance with the flow of liquid. Dr Browns Product Information: Our Dr. Browns BPA Free bottle features a patented two-piece internal vent system that works unlike any other bottle design. As the baby feeds, air is channelled from the teat collar through the vent system, bypassing the breast milk or formula, to the back of the bottle. Air never mixes with the breast milk or formula which minimises oxidation and helps maintain essential nutrients like vitamins C, A and E. B abies feed more comfortably because the vent system allows them to nurse without fighting the negative effects of a vacuum or the discomfort of ingesting air bubbles. This helps to reduce feeding problems like colic, burping, and wind. The breast milk or formula flows freely, without teat collapse. No vacuum, no bubbles, no teat Collapse!