Optics Designed for Brighter Views. PROSTAFF 3S features an optical system created from lead-and-arsenic-free Eco-Glass. Multilayer coatings, which provide high light transmittance across the entire visible light spectrum, are applied for bright images. High-reflectivity silver-alloy mirror coating applied on the mirror surfaces of the prisms for a bright and clear view. Long Eye Relief. Nikon has manufactured the PROSTAFF 3S binoculars, as well as many other of its optics, with a high-eyepoint design for long eye relief without vignetting. This provides a clear field of view for everyone, even when the user is wearing eyeglasses. Rubber-Armored Design. PROSTAFF 3S has a rugged rubber-armored coating to provide a non-slip grip, even in the wettest conditions. Waterproof and Fogproof. PROSTAFF 3S binoculars are Nitrogen filled and O-Ring sealed for complete waterproof and fogproof performance.