Principle:In order to see the details of a small object, it is necessary to move the object to the eye, so as to increase the of and form a larger on the retina. when the object is too to the eye, it can not see clearly. In other words, to be aware of , not only should the object have a good enough to the eye, also should take the appropriate distance. Obviously, for the eyes, these two requirements are mutually restrictive. If a convex lens is placed in the front of the eyes, this problem can be solved. Convex lens is the simplest magnifying glass, which is a simple optical instrument to help the eyes observe Small objects or details. Magnification: 10X Colour:black Material:plastic Size:41 x 44 x 45mm Lens diameter: 20mm Package Contents: 1 x Scale magnifier Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.