Blending many of the best features from the Viper PST and HS riflescopes, the Viper HST is ideal for a wide range of shooting applications. Built from a single piece of aircraft grade aluminum, creating a tough foundation for this optic, it is O-ring sealed and argon gas purged for waterproof, fogproof reliability. Vortex's XR fully multi-coated lenses crafted from XD low dispersion glass ensure maximum light transmission with unparalleled resolution and color fidelity.