Sun Optics USA Tri-Rail Tactical Mil-Dot Series Picatinny Rifle Scope with Picatinny Illuminated Reticle (4 x 28-Inch) Integrated mounting system and tri-rail equipped Fast focus eyepiece and mil-dot reticle Sharp edge-to-edge clarity at every power Dry nitrogen filled and 100% waterproof, shockproof & fogproof Precision ground, fully coated optics