HVML-2.5 Replacement Lens, Binocular Headband Magnifier Replacement Prismatic Glass 2.5x lens with 8" Focal length/working distance for binocular headband magnifier, these will fit our HVM-3 and HVM-4 models they will also fit many other headband magnifiers including OptiVISOR® Brand. They are easily replaceable simply push out mounting pins, and install new lens plate, and push in mounting pins to lock in new lens. Each lens comes with new pair of lens mounting pins. If you currently have a Donegan Optivisor all of your lenses and accessories will fit this model.