These optical lens for physics teaching adopt glass materials, safe and to support long term using. These concave lens and convex lens can help you earn and understand more specifically and obviously how to find the principle of light convergence. Small size, easy to take, use and clean, the optical lens kit can let you have . 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 - Glass material made, these optical lens are with high durability to support long term using. - Well polished, smooth surface, the optical lens will not hurt hands when used, you can use rest assured. - Light weight and compact size, the glass optical lens are easy to carry and store, you can feel the great convenience. - Clear optical lens can help you learn and understand more specifically how to find the principle of light convergence. - Practical teaching tools for you to learn about the properties of light, also good for physics teachers to conduct teaching. 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)