Made from high quality extra durable natural latex. Medium feed hole suitable for use with milk. Nuk teats have an unique air system which helps combat the problem of swallowing air during feeding, to help reduce colic. An air vent helps prevent the teat collapsing and when feeding it is important the the vent is under the baby's nose. The feed hole points upward so the milk mixes with saliva to aid digestion. The flat slender neck and underside of the teat encourages a sucking action which aid baby's jaw and palate development and also the design helps widen the jaw allowing correct spacing for tooth development.