Description of Ajax Scientific Double Convex Bi Convex Spherical Science Education
Double-convex (bi-convex) lens for demonstrating optical principles and effects for students. Two outwardly curved surfaces converge light rays to a point. Focal length is 100mm. Lens is 50mm in diameter. Made of polished glass with ground edges.
Keep this in your travel bag as a splinter removal tool and additional fire source. There are no obvious flaws, the edges are a little rough, but that's not critical.