For over a decade, Endurance ED optics have been renowned for incredible performance and reliability. Now, with the introduction of the Marine range, we have grown upon this award winning selection with optics that are specifically designed for marine and boating applications. With a range of models to choose from, the Marine Optics family feature binoculars and monoculars to suit any requirement. Advanced BAK-4 roof prism optical systems make far more compact, modern and lightweight optics than the industry norm. Built-In Compass Rangefinder Reticle Display For Distance Calculation 7x Magnification Perfect For Marine Applications Extra-Low Dispersion (ED) Glass Phase Corrected High Resolution Phase Corrected BAK-4 Roof Prisms Twist-Up Eye Cups With Position Stops Stay-On Lens Covers Floating Wrist Strap Nitrogen purged. Waterproof. Fog proof. Hawke No-Fault Lifetime Warranty. Rangefinding Reticle Selected models have a built-in Rangefinding Reticle alongside the compass within the optical view. The rangefinding reticle can be used to calculate distance between you and the object you are looking at. This can be extremely important in nautical environments assisting as a visual check and as a failsafe to on-board navigation systems. The rangefinding reticle is made up of a grid-like pattern of lines that are segmented into Milliradians, known sometimes as Mils. A milliradian is a unit of angle that can be used to calculate the distance of a known sized object. Rangefinding Equation (metric) If you were looking at a lighthouse on shore that you knewto be 20m tall and looking through the rangefinding reticle it measured 50 milliradian: Distance = 20 x 1000 / 50 = 400mThe lighthouse is 400 m away. Rangefinding Equation (imperial) If you were looking at a lighthouse on shore that you knewto be 60ft tall and looking through the rangefinding reticle it measured 50 milliradian: Distance = 60 x 333 / 50 = 400ydsThe lighthouse is 400 yards away. Product Type Monocular Product Type Monocular Product Range Endurance ED Marine Product Range Endurance ED Marine Objective Lens 42mm Objective Lens 42mm Color Blue Color Blue Magnification 7x Magnification 7x Optical System System H5 Optical System System H5 Field of View 393ft @100yds 131m @100m Field of View 393ft @100yds 131m @100m 393ft @100yds 131m @100m Field of View 7.5° 7.5° Eye Relief 0.7in 17mm Eye Relief 0.7in 17mm 0.7in 17mm Exit Pupil 0.24″ 6mm Exit Pupil 0.24″ 6mm 0.24″ 6mm Lens Coating Fully Multi-Coated Lens Coating Fully Multi-Coated Apparent Field of View 53° Apparent Field of View 53° Interpupillary Distance ● ● Interpupillary Distance ● ● ● Close Focus 6.6ft 2m Close Focus 6.6ft 2m 6.6ft 2m Prism Type Roof Prism Type Roof Prism Glass BAK 4 Prism Glass BAK 4 Eye Cups Twist-Up Eye Cups Twist-Up Diopter Type Eye Piece Diopter Type Eye Piece Tripod Mounting Thread Yes (¼" - 20 UNC) Tripod Mounting Thread Yes (¼" - 20 UNC) Length 6.3″ 159mm Length 6.3″ 159mm 6.3″ 159mm Width 3.1″ 80mm Width 3.1″ 80mm 3.1″ 80mm Weight 14.3oz 405g Weight 14.3oz 405g 14.3oz 405g