kid kanteen baby bottles feature a medical-grade, silicone nipple that is more than 2 inches in diameter at the base and has variable thicknesses so it feels more like the real thing. as your baby sucks, the long nipple adjusts, mimicking the way a human breast reshapes during breastfeeding, ensuring proper placement in the mouth, and promoting correct oral development and healthy teeth. the nipple also features a double venting system, which is designed so your baby is swallowing liquid, not air, helping reduce colic and promoting healthy digestion. available in 3 flow rates: slow, medium and fast. sold in 2-packs.