In Canada and the United States, a football (also called a pigskin) is a ball, roughly in the form of a prolate spheroid, used in the context of playing gridiron football. Footballs are often made of cow hide leather, as such a material is required in professional and collegiate football. Footballs used in recreation, and in organized youth leagues, may be made of rubber or plastic materials (high school football rule books still allow inexpensive all-rubber footballs, though they are less common than leather).