Marathon Binocular 10 x 25 has a field of view expressed in feet at a distance of 1,000 yards or meters at 1,000 meters, and is the width of the visible area that can be seen without moving the binoculars. The 18.5mm eye relief is the optimal distance from the eyepiece to your eye, or the focal point where the light passes through the ocular lens. Great to use even with eyeglasses. The product is nitrogen filled for fog-proofing, and it is also water-resistant. Additional Features- • Built-in tripod mount. • Neck strap, eye-cup protectors, objective lens protectors, carrying case, lens cloth and instructions included.