Kid Kanteen Baby Bottles feature a medical grade silicone nipple that is over 2 inches in diameter at the base and varying thicknesses, so it feels more like the real thing. As your baby sucks, the long nipple adjusts, mimicking the way the human breast adjusts during breastfeeding, ensuring proper mouth placement and promoting proper oral development and healthy teeth. The nipple also features a double vent system, which is designed so your baby swallows fluids, not air, helping to reduce colic and promoting healthy digestion. Available in 3 flow levels: slow, medium and fast. Sold in packs of 2.