Donegan ELD 2.5-1 Watch And Clock Makers Double Eye Loupe, 4x-10x Magnification Double-eye loupe magnifier provides hands-free magnification and viewing for a variety of applications such as jewelry-making, watch-making, clock-making, needlework, electronic inspection, book-reading, print inspection, and stamp-collecting Available in multiple lenses that provide a specific magnification power (X), depending on the distance from the object A dioptric number and a magnification number are not the same thing. Diopter strength represents a specific magnification power (X). For example, a 5-diopter provides 2.5X magnification (at a distance of 8) Two separate lenses attach to prescription glasses, can be used one in front of the other, pivot to the side when not in use, and align in front of prescription lens when magnification is needed Optical glass lenses are ground and polished into prismatic lenses for quality and clarity