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.