This high-quality lens and prism set is useful for teaching a wide variety of optical principles. You get three lenses and four prisms. The lenses are polished on all surfaces. Sizes vary from 52mm to 88mm in length. Lenses include double concave, double convex, and semicircular. Prisms include large right angle, trapezoid, right angle, and equilateral. 7 piece acrylic set