Vortex Razor HD 5-20x50 Riflescope — First Focal Plane Vortex breaks new ground with our Razor HD tactical riflescopes. Built literally from the ground up to meet the demanding needs of precision shooters. The Razor HD 5-20x50 is a state-of-the-art long-range performer built on a solid 35mm one-piece tube and packed with more than a dozen unique performance and optical features—including a precision-etched first focal plane reticle. Optical Features First Focal Plane Subtensions remain consistent throughout magnification range. APO Objective Lens System Corrects color across the entire visual color spectrum—virtually eliminating chromatic aberration across the entire field of view. Optically Indexed Lenses Deliver optimum image sharpness and brightness with true reticle use for full ranging and holdover from edge to edge because of computer-controlled alignment during construction. HD Lens Elements Premium (High Density) extra-low dispersion glass delivers the ultimate in resolution and color fidelity, resulting in High Definition images. XR Lens Coatings Vortex proprietary XR fully multi-coated lens coatings increase light transmission for maximum brightness. Construction Features 35 mm Tube Provides more internal room to accommodate a greater range of windage and elevation adjustment to accurately dial longer-range shots. One-Piece Tube Maximizes alignment for improved accuracy and optimum visual performance as well as strength and waterproofness. Aircraft-Grade Aluminum Construction from a solid block of 6061-T6 aircraft-grade aluminum delivers increased strength and rigidity. Waterproof O-ring seals prevent moisture, dust, and debris from getting inside the tube for reliable performance in all environments. Fogproof Filled with argon gas to inhibit internal fogging over a wide range of temperatures.