Optivisor is a precision binocular headband magnifier that provides unrestricted efficiency while reducing eye strain, leaves both hands free, and allows three dimensional vision. Can be worn over prescription or safety eyeglasses.Genuine Optivisors are the best headband magnification in the world. Leather-lined headband adjusts to any head size. Lenses are crafted from the highest quality optical glass. Comes with a #4 lens. Magnification 2X at 10in. You'll love it and you'll never have to buy another.