High-reflectivity silver-alloy mirror coating applied on the mirror surfaces of the prisms for a bright and clear view. Multilayer-coated lenses for bright images. Long eye relief design ensures a clear field of view, even for eyeglass wearers. Lead- and arsenic-free glass is used for all lenses and prisms. Turn-and-slide rubber eyecups with multi-click facilitate easy positioning of eyes at the correct eyepoint. Waterproof (up to 1m/3.3 ft. for 10 minutes) and fog-free with O-ring seals and nitrogen gas. Rubber armouring for shock resistance and a firm, comfortable grip. Lightweight body uses fibreglass-reinforced polycarbonate resin.