Marathon 7x50mm BAK-4 Prism Binocular Black. Engineered with a premium BAK-4 prism it offers an excellent viewing experience with superior light transmission and less peripheral light being lost due to internal reflection. This binocular is built to thrive in any environment; waterproof and submersible to a depth of 0.5m for up to 20 minutes and featuring a nitrogen-filled case to prevent fogging of the lenses during changes in heat or humidity. Specifications for Marathon 7x50mm BAK-4 Prism Binocular: Manufacturer: Marathon Color: Black Magnification: 7 x Objective Lens Diameter: 50 mm Prism Material: BAK-4 Eye Relief: 0.9 in Exit Pupil: 5 mm Field of View Linear: 365 ft at 1000 yds Optical Coating: Fully Broadband Multi-Coated Binoculars Focus System: Center Focus Weight: 1.5 lb Package Type: Box Package Contents: Marathon 7x50mm BAK-4 Prism Binocular Marathon BI030024: 7x50mm BAK-4 Prism Binocular Black