Large front lens diameter for brighter and wider field of view: Nikon Aculon A211 16x50Features: Multi-coated lenses for bright and sharp image; Adjustable rubber eyecups simplify eye positioning; Aspherical eyepiece lenses minimize image distortion over the entire lens surface; Rubber armor provides shock resistance and comfortable handling; Magnification: 16 -x; Objective lens diameter: 50 mm; Lens speed: 9.6; Exit pupil distance: 12.6 mm; Close focusing distance : 9.0 m; Real field of view: 4.2° -Apparent field of view: 60.8°; Field of view at 1.000 m: 73 m; Exit pupil: 3.2 mm; Interpupillary distance: 56 - 72 mm.