This is the #46 Telesight® 2-1/2X at a 6-2/3″ Focal Distance (measured from eye, not from lens). Binocular eye loupe mounted in half-frames, no heavier than ordinary eyeglasses. The half-frames stay in place; just lower lenses for magnification and flip up when finished. Lens is optical quality injection-molded acrylic treated with abrasion-resistant coating. For use without prescription glasses or use the clip-on style for use with prescription glasses.