The Ncstar GEN3 Ultimate Sighting System USS AR-15 3-9x40 BDC riflescope combo with Red Micro Dot optic is calibrated for the AR15, M4 .223 rifles 1 ½" centerline height. The AR optics Micro Dot Sight is mounted directly to the rifle scope body inside an armored micro dot mount. The AR-15 3-9x40 compact rifle scope features a modern new look and enhanced features with an illuminated MIL-Dot reticle in Red & Blue with an electronic control panel. The scope has Bullet Drop Compensator, a large magnification ring, with quick focus ring, uses a standard AA battery, and a quick release Picatinny mount. It includes a Red Dot optic DDAB mounted directly to the top of the scope body, inside an armored micro dot mount. The Electronic Control Panel turns on/off the illuminated MIL-Dot reticle, adjusts the brightness level of the illuminated MIL-Dot reticle, changes the reticle color from Blue or Red. The GEN3 Ultimate Sighting System whole Ocular body functions as a large Magnification ring. There is also an adjustable reticle focus ring at the end of the ocular lens. The scope has a Low Profile Elevation Turret with a Bullet Drop Compensator (BDC) calibrated for M193 55gr. FMJ Mil-Spec ammo. It uses a single standard AA battery (included) for long battery life and easy use. Auto-Locking Quick Release Mount, fits Weaver/Picatinny/ MIL-STD 1913 type rails.