Vortex Optics Viper PA Second Focal Plane Riflescopes The Viper 6.5-20x50 is built on a 30mm main tube with a hard anodized finish providing a rugged, tough hunting riflescope. Originating from the US Marine Corps, the Mil-Dot reticle is useful for helping to estimate range, wind age and bullet holdover. Incorporating our premium, fully multi-coated, extra-low dispersion lenses brings excellent resolution and color fidelity. The XR coatings provide enhanced light gathering capability while Armortek coating protects the lenses. Capped reset turrets allow quick re-indexing of the turret to zero after sighting in the riflescope. Side knob parallax adjust allows quick and easy parallax adjustments with range numbers visible while in the shooting position. The fast focus eyepiece allows for quick and easy reticle focusing while the MAG-Bar allows rapid, easy changes in magnification. The Viper 6.5-20x50 riflescope is ideal for long range, predator/varmint, and target applications. O-ring sealed and argon purged, the Viper provides fog proof and waterproof performance.