Fully multi-coated lens: Effectively reduces reflected light and increases the transmission of light giving you a brighter image than normal single coated lenses Regardless of how heavy the rain is coming down or an accidental drop in the water, this sealed and gas-purged optic will remain waterproof. Nitrogen gas is used to purge air from the optic to help maintain internal fog-proof and waterproof capabilities Fog proof and shock proof. Aircraft grade aluminum tube Brand Athlon Optics Color Black Style Tactical Hunting Sport Hunting Objective Lens Diameter 40 Millimeters