National Geographic 10x25 Compact Roof-Prism Binoculars. Made of fully-coated BK-7 glass the quality optics magnify subjects 10 times their standard observable size to reveal unexpected details and have a nice-sized 25mm aperture that is perfect for daytime observation. Water-resistant and rubber-coated for protection against minor bumps these binoculars offer a textured central focusing wheel in addition to diopter adjustment capability that ensures both eyes achieve proper focus. They also come with a case strap and cleaning cloth. Specifications for National Geographic Compact Roof-Prism Binoculars: Manufacturer: National Geographic Color: Black Magnification: 10 x Objective Lens Diameter: 25 mm Prism System: Roof Field of View Linear: 97 ft at 1000 yds Binoculars Focus System: Center Focus Twilight Factor: 15.81 Package Type: Box Included Accessories: Lens Covers Case Strap Magnification Type: Fixed Package Contents: National Geographic Compact Roof-Prism Binoculars National Geographic 80-11025: 10x25 Compact Roof-Prism Binoculars