This magnifier has a top mount thumb rest which promotes a more natural hand position and creates balanced weight distribution between the lens and handle. The 2x to 4.5x bifocal lens and extremely lightweight design is perfect for extended reading times or for those with limited strength. A distortion-free view is provided by the crystal-clear acrylic lens. Details:Acrylic lens2x power magnification4.5x power spot lensTop mount thumb rest