National Geographic Foldable Roof-Prism CP Binoculars 8x21. These pocket binoculars feature a roof prism design that is easy to manipulate for proper eye distance and quality optics made of fully-coated BK-7 glass. Offering a field of view of 413 feet at 1000 yards these binoculars magnify subjects eight times their standard observable size making them an ideal beginner tool for bird watching or other wildlife observation. Other features include a textured central focusing wheel rubber eyecups for comfort and diopter adjustment capability that ensures both eyes achieve proper focus. The binoculars also come with a case strap and cleaning cloth. Specifications for National Geographic Foldable 8x21mm Roof Prism Binoculars: Manufacturer: National Geographic Color: Black Magnification: 8 x Objective Lens Diameter: 21 mm Binoculars Focus System: Center Focus Twilight Factor: 12.96 Package Type: Clam Pack/ Plastic Included Accessories: Lens Covers Case Strap Magnification Type: Fixed Package Contents: National Geographic Foldable Roof-Prism Binoculars National Geographic 80-10821-CP: Foldable Roof-Prism CP Binoculars 8x21