Optivisor DA10 - 3 1/2X features a working distance of 4" and has a magnification of 3 1/2X. Optivisor is our best selling, most requested, brand of headband magnifiers. It features a dial adjustment headband to fit any head size. Well-made magnifier is lightweight and durable, and fits over eyeglasses. Adjustable pivot assembly on visor can be set to desired tension, so it will stay in place when tilted.