Magnifiers are devices used to enlarge the visual appearance of an object or image. Magnifiers come in a variety of styles such as hand-held, headband, standing, clip-on, eye loupe, and those that hang in a necklace form, or fit in a trouser pocket. Magnifiers are commonly made of plastic or glass. They can have one or more lenses with varying magnification abilities, and can have a binocular configuration with a single lens, or two separate lenses. They are sometimes used with LED or fluorescent light sources to help control viewing capabilities. Magnifier ability is often expressed as magnification at a specific length. For example, 1.75X at 14” means that when a magnifier is held at 14” from a viewer’s eyes, the object will be magnified 1.75 times (X) its actual size. As magnification increases, viewing areas and focal length decrease. Magnifiers sometimes have a diopter number, expressed as + or -D, which is a measurement of strength (or power) of the lens. Some magnifiers are marked with a dioptric number on the lens. A high diopter number has a higher magnification than a low diopter number. Aspheric magnifiers, unlike spheric magnifiers, produce a sharp image to the edge of the lens for less distortion. Magnifiers are widely used in jewelry inspection and fabrication, watch-making, needlework, artwork, fly-tying, electrical inspection, reading, print inspection, and stamp-collecting. Donegan Optical manufactures precision visual devices such as magnifiers and optical loupes. The company, founded in 1952, is headquartered in Lenexa, KS.Country of origin: Japan. Chrome-plated brass case. One 15X and one 20X lens system. Magnfier with two swing-out double lens systems.Item Dimensions LxWxH: 2.72 x 1.5 x 0.98 inches. Lens Material: Glass. Item Weight: 0.5 Pounds. Batteries Required?: No. Brand: Donegan Optical. Best Sellers Rank: Camera Loupes. : B000EM98K2. Manufacturer: Donegan Optical. Date First Available: April 20, 2010. Our Recommended age: 8 years and up. Product Dimensions: 2.72 x 1.5 x 0.98 inches; 8 Ounces.