The Sightron S-TAC3-16X42 features 3-16X magnification with an objective diameter of 42mm and tube diameter of 30mm. The target-style turrets offer 1/4 MOA adjustments at 100 yards and are resettable to zero. This scope features Sightron?s unique ExacTrack windage and elevation adjustment system, applying a proper alignment between the adjustments and the erector tube. Side focus parallax allows easy adjustment and focus from minimum distance to infinity. The Zact-7 Revcoat multi-coating provides maximum optical quality and light transmission. This scope is waterproof, shockproof, and nitrogen gas charged.Features:Fast focus eyebell;Duplex reticle - Second focal plane;1/4 MOA clicks at 100 yds;3.8 - 4.1 in. of eye relief;30mm tube diameter