HVM-4 3.5xl This headband magnifier is our HVM-4 Premium Binocular Headband Magnifier Visor with 3.5x and 4" Focal Length, and extra 5x eye loupe one eye. This Magnifier is best for very close detailed work with the 4" working distance. For longer working distance models please see the 2.5x,2x, or 1.5x. This headband is fully adjustable to fit any size quickly and easily, visor is also adjustable +/- 60 degrees either way making it easy to flip up and out of the way of the line of sight at anytime. The HVM-4 premium features an aluminum alloy headband pivot mechanism as well as scratch resistant glass prismatic lenses, lightweight durable impact resistant visor shell more suitable for the industrial environments. The 3.5x glass prismatic lens gives you an close working distance of 4" for most repetitive applications and hands free magnified view. 3.5x is the highest magnification for binocular (both eyes) magnified view, anything beyond 3.5x and the focal length is too close to see with both eyes ( your eyes would go crosseyed closer than 4"). This headband magnifier can be worn over eyeglasses and most safety glasses.