Features and Functions: Eco-Glass Optics: Lead and Arsenic-Free BAK4 Porro Prisms Fully Multicoated Optics Wide Angle Viewing Nitrogen-Filled Fogproof / Waterproof Turn-and-Slide Rubber Eyecups 17mm Eye Relief Rubber Armored Housing Description: The 10x50 Action Extreme ATB Binocular from Nikon is a general purpose optic that offers a weather-sealed housing and slip-resistant handling. Additionally, Action Extreme ATB binoculars are equipped with a fully multicoated optical path that displays a 59.2° apparent viewing angle. Nikon's Eco-Glass optics are made of environmentally-friendly lenses and prisms that don't contain lead or arsenic. Complementing the image quality and nitrogen-filled housing are Turn-and-Slide eyecups and a 17mm eye relief, allowing the viewer to set a comfortable viewing distance even while wearing eyeglasses.