Waterproof (up to 2m/6.6 ft. for 5 minutes) and fog-free with nitrogen gas. Aspherical eyepiece lens eliminates image distortion. High-eyepoint design provides a clear field of view for those who wear eyeglasses. Close focusing distance 2.8m. Multilayer-coated lenses for brighter images. Turn-and-slide rubber eyecups facilitate easy positioning of eyes at the correct eyepoint. Eco-glass optics are free of lead and arsenic.