Bergeon 2611-TB x2.8 is made of synthetic material. For efficient work, the strength (magnification) of the eyeglass must be adapted to each individual job. A reliable magnification should be used for ordinary work, this avoids eyestrain! Eyeglasses with a high degree of magnification are to be used for limited periods only.As you will see, our eyeglasses are available different strengths; you can thus choose the one that suits you best. As these glasses are inexpensive, we would advise you to keep a set giving different degrees of magnification. Lense: biconvex Magnification: 2,8x Number: 3,5 Ø Diameter: 25,0 mm Color: White