This is a physics optical lens applied to understand the principle of light convergence more intuitively. Adopting good workmanship, safe and support for long period to use. Small size, easy to use, these physics teaching lens can stimulate students' cognitive ability in physics, giving you more convenience. Features -Color:multi -Material:Plastic, iron, glass -Size:14.30X4.50X1.00cm/5.62X1.77X0.39in -focal length: 10cm - Made of good workmanship, these optical lens is safe, can support for long period to use. - Practical convex lens can effectively explain the knowledge of optics with experiments. - Science teaching tools can stimulate students' cognitive ability in physics, also can be a good helper in teaching. - Handheld design, the physics optical tool is easy and comfortable to hold on hand. - Easy to use and clean, save your time and efforts to let you have satisfying using feeling. Package list: 1 x Convex Lens