Clip-on magnifiers are designed to provide spectacle weavers with hands-free magnification. Fits most eyeglass frames (Bridge: 25mm, Jaws open 15mm). Lightweight. Lens is set 2 inches from eye, allowing for a more comfortable working distance. When not needed, the lens can be flipped up and out of the way. Lenses are interchangeable for different magnification needs. Magnification: 3x. Lens Type: Aspheric. Lens Material: PXM Plastic with Cera-Tec Coating. Fits over prescription eyewear.