The nipple is made of 100% natural rubber latex – which is soft and flexible. The nipple is equipped with a vent hole, letting out the air to make the teat shape as natural as possible. Because of the natural material, variations in color and clearness may occur – remember to replace within 4-6 weeks of regular use! The shield is convex which allows airflow to ventilate the delicate baby skin. The shield is made of polypropylene (PP), a very light plastic material with high strength, and is very wear resistant.