The Trijicon ACOG (Advanced Combat Optical Gunsight) is a fixed power, compact riflescope with an illuminated reticle pattern for use in bright to low/no light. The ACOG is designed to be extremely durable and reliable. Combining traditional, precise distance marksmanship with CQB speed, many variants include a bullet drop compensated (BDC) reticle. Every feature of its design was chosen for a single purpose: to provide increased hit potential in all lighting conditions. The Trijicon ACOG/RMR combo is the ultimate aiming solution for both Close Quarter Battle (CQB) situations and longer distance shots requiring additional magnification. This dual-sighting system gives the shooter a distinct tactical advantage with the option of the Trijicon ACOG and the RMR Type 2 Sight. With the quick target acquisition of the RMR sight and the precise aiming capabilities provided by the magnified Trijicon ACOG, the shooter has the ability to select the proper aiming solution for the situation at hand. Also, the RMR offers similar rugged construction as the ACOG for the situation at hand. Truly the best of both worlds. The Trijicon ACOG ECOS is the ultimate sight for both CQB situations and longer distance shooting where accuracy and pinpoint bullet placement are required. This dual-sighting system gives the shooter a distinct tactical advantage with the option of either the Trijicon ACOG or the RMR Type 2 Sight. With the quick target acquisition of the RMR Sight or the precise aiming capabilities provided by the magnified 4 power Trijicon ACOG- the shooter has the ability to select the proper aiming solution for the situation at hand- truly the best of both worlds. No tools are needed for windage and elevation adjustments because the ECOS also features external windage and elevation adjusters, making it waterproof up to 11m without caps. Comes with a TA51 Flat Top mount.