Nikon 7566 8x42 EDG Binocular (Black) Nikon's ED (Extra-low Dispersion Glass Lenses with Dielectirc High-Reflective Multilayer Prism Coatings Incorporates phase-correction coated roof prisms to enhance resolution Field Flattener Lens System O-ring sealed and dry nitrogen filled to handle the toughest conditions on the planet (up to 10 minutes submersed at 16.4 ft) Magnesium-Alloy Body - cuts weight without sacrificing durability