Donegan AL-13 Optical Grade Acrylic Lens Plate for The OptiVisor And AccurSite Series, 1.75x Magnification, 14" Focal Length Replacement lens plate with 1.75X magnifying lens for hands-free viewing using OptiVisor or AccurSite binocular visor (sold separately) Optical-grade acrylic prismatic lens for improved focus and reduced eye strain 14" focal length