Trijicon ACOG TA01 Scope is an ACOG(Advanced Combat Optical Gunsite) 4x32 Scope w/ tritium glow in the dark Illumination. It fits the M16/AR15 rifles equipped with fixed carry handles. The Trijicon ACOG TA01 4x32 Scope was designed specifically for the M16/AR15 rifles. The reticle bullet drop compensator and range finding stadia lines are based on the trajectory of the 5.56/.223 round . The ACOG TA01 is a compact and ruggedly designed scope and a valuable addition to any rifle - The Trijicon ACOG TA01 is considered one of the best optical sights issued to any Armed Forces. The finest optical design, 100% U.S. made components and Mil-C-14806A multi-layer coated glass elements make the Trijicon ACOG TA01 the ultimate telescopic sight. The black daytime reticle in the Trijicon TA01 ACOG Scope glows red at night and in low light due to its tritium composition. Forged aircraft aluminum housings - the same material as the M16 receivers - are precision machined and hard anodized to match the finish of the M16. Unique to the Trijicon ACOG is its internal adjustment capability - only the prism housing moves - making this the most rugged scope available. The ACOG will withstand exposure to temperature extremes, salt spray, fog, fungus, humidity, sand, dust, shock vibration and a free fall drop onto a hard surface. Aerospace seals make the Trijicon ACOG TA01 scope waterproof to depths greater than 500 feet. A hole through the M16 integral base permits use of the iron sights without removal of the scope. It can be attached to the carrying handle with one or two screws (2nd screw is optional). The user does not need to make any special adjustments between shots at different ranges. The ranging is already built into the reticle pattern (parallax free along its vertical axis). The width of the horizontal lines corresponds to the height of a 19 inch silhouette at that range.