The Physiological Teat with Anti-Colic Valve is soft and elastic, and it simulates the physiology of mother's breast as much as possible. The following features makes it unique: Ribbed Rings: Increase the natural elasticity of natural latex rubber , Special Length: Specially designed to stimulate the nipple during sucking , Large Base: Ensures maximum support for baby's lips and helps sucking , Anti Colic Valve: Avoid swallowing of air and helps reduce colic, hiccups and regurgitation. It comes in a pack of 2 pcs. It is used with Chicco feeding bottles. It comes in 3 types of flows: Regular Flow, Medium flow & Fast Flow. Made with silicone.