The hyperbolic paraboloid and the hyperboloid of one sheet are doubly ruled surfaces. A hyperboloid of one sheet is "projectively" equivalent to a hyperbolic paraboloid. A paraboloid is either elliptic or hyperbolic. Hence the hyperbolic paraboloid is a conoid. In particular, Pringles fried snacks resemble a truncated hyperbolic paraboloid. The consistent saddle shape is mathematically known as a hyperbolic paraboloid. Separate transmitting and receiving dipoles were at the focus of a 3-meter paraboloid reflector. It was constructed of eight laminated wood Hyperbolic paraboloid shells. The roof structure was a "hyperbolic paraboloid" positioned on cement bastions. The Pringles potato chip or crisp is an everyday example of a hyperbolic paraboloid shape. A third type of ruled surface is the hyperbolic paraboloid. In this position, the elliptic paraboloid opens upward. If , an elliptic paraboloid is a "circular paraboloid" or "paraboloid of revolution". Strictly, the three-dimensional shape of the reflector is called a "paraboloid". If the reflector were a rigid paraboloid, the focus would move as the dish turns.