American Educational 6 Piece Glass Lens Set Set of six glass lenses with different curvatures for demonstrating optical principles and effects for students One each of the following lenses: double-convex, plano-convex, double-concave, plano-concave, concavo-convex, and convexo-concave Double-convex, plano-convex, and concavo-convex lenses converge light rays to a point, and convexo-concave lenses diverge light rays from a point Each lens is 50mm in diameter