Clamp-On Table Desk Magnifier Magnifying Lamp Light 3 Diopter Swing Arm White Powerful optically ground 3 diopter magnifying glass lens, brings small work up close. Glass measures 4" inches in diameter. Versatile flexible arm extends up to 36" inches. Fully adjustable to any position with steel springs and tension control knobs. Fully adjustable to any position with steel springs and tension control knobs. Offers excellent magnified lighting and hands free use for hobbies, close precision inspections, reading and many other uses for home or office.