These are some physics optical lens which can be applied to understand the principle of light convergence more intuitively. Made from glass materials, they are safe and for long period to use. Small size, light weight, easy to use and take, these physics teaching lens can stimulate cognitive ability in physics, let you have satisfying using feeling. Features -Color:Transparent -Material:Glass -Size:6.00X1.60X1.00cm/2.36X0.63X0.39in -Size:6.00X3.00X1.00cm/2.36X1.18X0.39in -Size:6.00X3.50X1.00cm/2.36X1.38X0.39in - Made from glass materials, these optical lens are professional and , can be used for long time. - With different shape, practical convex and concave lens can effectively explain the knowledge of optics with experiments. - Physics teaching tools can stimulate cognitive ability in learning, also can be a good helper for teachers to teach. - These glass optical lens are good tool to show how different aspects of lenses and light passing through and bending, very practical. - Smooth surface, the transparent optical lens are easy to use and clean, save your time and efforts largely. Package list: 1 x optical lens(cylindrical convex lens) 1 x optical lens(cylindrical concave lens) 1 x optical lens(semicircle lens) 1 x optical lens(rectangle lens) 1 x optical lens(equilateral triangle lens)